feat: clone Opal's rules feature with hard block enforcement

Rebuild the app around recurring screen-time blocking rules modeled on
Opal's My Apps tab:

- Onboarding with FamilyControls Screen Time authorization
- Apps home with Blocked Apps tiles and live rule cards
- New Rule sheet: Schedule/Time Limit/Open Limit types + preset gallery
- Rule editors: time windows (incl. overnight), day picker, app selection
  via FamilyActivityPicker (Block/Allow Only), rename, Hold to Commit
- Hard Mode: active hard rules cannot be edited, disabled, deleted, or
  unblocked until their window ends; soft rules pause until next window
- Shield enforcement through per-rule ManagedSettingsStore + RuleEnforcer
- 73 unit tests (Swift Testing) + 16 UI tests (XCUITest) with launch-arg
  harness for in-memory storage, mocked authorization, seeded scenarios
- docs/RULES_FEATURE_SPEC.md: spec derived from the reference recording

Known gap: background window transitions and time/open-limit thresholds
need a DeviceActivityMonitor extension; shields currently sync while the
app is running.

Severed/Services/LaunchConfiguration.swift

@@ -0,0 +1,45 @@
+//
+//  LaunchConfiguration.swift
+//  Severed
+//
+
+import Foundation
+
+/// Launch-argument configuration used by UI tests: in-memory storage, mocked
+/// Screen Time authorization, forced onboarding state, and seeded scenarios.
+struct LaunchConfiguration: Equatable {
+    enum SeedScenario: String {
+        /// One actively blocking rule ("Work Time") and one upcoming rule ("Sleep").
+        case standard
+        /// An actively blocking Hard Mode rule ("Locked In") plus an upcoming rule.
+        case hardModeActive = "hard-mode-active"
+    }
+
+    var isUITesting = false
+    /// Forces the onboarding-completed flag at launch. Nil leaves stored state alone.
+    var onboardingCompleted: Bool?
+    var seedScenario: SeedScenario?
+
+    static let uiTestingFlag = "-ui-testing"
+    static let onboardingCompletedFlag = "-onboarding-completed"
+    static let onboardingRequiredFlag = "-onboarding-required"
+    static let seedScenarioPrefix = "-seed-scenario="
+
+    static func parse(arguments: [String]) -> LaunchConfiguration {
+        var config = LaunchConfiguration()
+        config.isUITesting = arguments.contains(uiTestingFlag)
+        if arguments.contains(onboardingCompletedFlag) {
+            config.onboardingCompleted = true
+        } else if arguments.contains(onboardingRequiredFlag) {
+            config.onboardingCompleted = false
+        }
+        if let seedArgument = arguments.first(where: { $0.hasPrefix(seedScenarioPrefix) }) {
+            config.seedScenario = SeedScenario(
+                rawValue: String(seedArgument.dropFirst(seedScenarioPrefix.count))
+            )
+        }
+        return config
+    }
+
+    static let current = parse(arguments: ProcessInfo.processInfo.arguments)
+}

Severed/Services/RuleEnforcer.swift

@@ -0,0 +1,43 @@
+//
+//  RuleEnforcer.swift
+//  Severed
+//
+
+import Foundation
+import Observation
+
+/// Turns the current set of rules into shield state: schedule rules with an
+/// active, un-paused window are shielded; everything else is cleared.
+///
+/// Time-limit and open-limit rules need a DeviceActivity monitor extension to
+/// react to usage thresholds in the background; they are persisted and shown
+/// in the UI but not yet enforced here.
+@Observable
+final class RuleEnforcer {
+    private(set) var blockingRuleIDs: Set<UUID> = []
+    private let shields: ShieldApplying
+
+    init(shields: ShieldApplying) {
+        self.shields = shields
+    }
+
+    /// Recomputes shields from scratch. Call on launch, on any rule change,
+    /// and periodically while the app is visible. Also expires stale pauses.
+    func refresh(rules: [BlockingRule], at now: Date = .now, calendar: Calendar = .current) {
+        var active: Set<UUID> = []
+        for rule in rules {
+            if let pausedUntil = rule.pausedUntil, pausedUntil <= now {
+                rule.pausedUntil = nil
+            }
+            guard rule.kind == .schedule,
+                  rule.status(at: now, calendar: calendar).isActive
+            else { continue }
+            active.insert(rule.id)
+            shields.applyShield(
+                ruleID: rule.id, selectionData: rule.selectionData, mode: rule.selectionMode
+            )
+        }
+        shields.clearShields(except: active)
+        blockingRuleIDs = active
+    }
+}

Severed/Services/SampleRules.swift

@@ -0,0 +1,65 @@
+//
+//  SampleRules.swift
+//  Severed
+//
+
+import Foundation
+import SwiftData
+
+/// Builds deterministic rules for UI-test scenarios, positioned relative to
+/// "now" so an active window is genuinely active whenever the test runs.
+enum SampleRules {
+    static func seed(
+        _ scenario: LaunchConfiguration.SeedScenario,
+        into context: ModelContext,
+        now: Date = .now,
+        calendar: Calendar = .current
+    ) {
+        switch scenario {
+        case .standard:
+            context.insert(activeRule(named: "Work Time", hardMode: false, now: now, calendar: calendar))
+            context.insert(upcomingRule(named: "Sleep", now: now, calendar: calendar))
+        case .hardModeActive:
+            context.insert(activeRule(named: "Locked In", hardMode: true, now: now, calendar: calendar))
+            context.insert(upcomingRule(named: "Sleep", now: now, calendar: calendar))
+        }
+    }
+
+    /// A schedule rule whose window started up to an hour ago and runs for
+    /// several hours, clamped so it never crosses midnight accidentally.
+    static func activeRule(
+        named name: String, hardMode: Bool, now: Date, calendar: Calendar = .current
+    ) -> BlockingRule {
+        let nowMinutes = minutesIntoDay(of: now, calendar: calendar)
+        let start = max(0, nowMinutes - 60)
+        let end = min(24 * 60 - 1, nowMinutes + 6 * 60)
+        return BlockingRule(
+            name: name,
+            hardMode: hardMode,
+            days: Weekday.everyDay,
+            startMinutes: start,
+            endMinutes: end
+        )
+    }
+
+    /// A schedule rule starting a couple of hours from now (possibly wrapping
+    /// past midnight, which simply makes it start tomorrow).
+    static func upcomingRule(
+        named name: String, now: Date, calendar: Calendar = .current
+    ) -> BlockingRule {
+        let nowMinutes = minutesIntoDay(of: now, calendar: calendar)
+        let start = (nowMinutes + 2 * 60) % (24 * 60)
+        let end = (start + 8 * 60) % (24 * 60)
+        return BlockingRule(
+            name: name,
+            days: Weekday.everyDay,
+            startMinutes: start,
+            endMinutes: end
+        )
+    }
+
+    private static func minutesIntoDay(of date: Date, calendar: Calendar) -> Int {
+        let components = calendar.dateComponents([.hour, .minute], from: date)
+        return (components.hour ?? 0) * 60 + (components.minute ?? 0)
+    }
+}

Severed/Services/ScreenTimeAuthorization.swift

@@ -0,0 +1,85 @@
+//
+//  ScreenTimeAuthorization.swift
+//  Severed
+//
+
+import FamilyControls
+import Foundation
+import Observation
+
+enum ScreenTimeAuthorizationStatus: Equatable, Sendable {
+    case notDetermined
+    case denied
+    case approved
+}
+
+/// Abstracts FamilyControls authorization so views and tests never touch
+/// `AuthorizationCenter` directly.
+protocol AuthorizationProviding {
+    var currentStatus: ScreenTimeAuthorizationStatus { get }
+    func requestAuthorization() async throws
+}
+
+/// Real Screen Time authorization via FamilyControls.
+struct FamilyControlsAuthorizationProvider: AuthorizationProviding {
+    var currentStatus: ScreenTimeAuthorizationStatus {
+        switch AuthorizationCenter.shared.authorizationStatus {
+        case .approved: .approved
+        case .denied: .denied
+        case .notDetermined: .notDetermined
+        @unknown default: .notDetermined
+        }
+    }
+
+    func requestAuthorization() async throws {
+        try await AuthorizationCenter.shared.requestAuthorization(for: .individual)
+    }
+}
+
+/// In-memory provider for unit and UI tests.
+final class MockAuthorizationProvider: AuthorizationProviding {
+    var status: ScreenTimeAuthorizationStatus
+    var requestShouldFail: Bool
+
+    init(status: ScreenTimeAuthorizationStatus = .notDetermined, requestShouldFail: Bool = false) {
+        self.status = status
+        self.requestShouldFail = requestShouldFail
+    }
+
+    var currentStatus: ScreenTimeAuthorizationStatus { status }
+
+    func requestAuthorization() async throws {
+        if requestShouldFail {
+            status = .denied
+            throw FamilyControlsError.authorizationCanceled
+        }
+        status = .approved
+    }
+}
+
+/// Observable authorization state for the UI.
+@Observable
+final class ScreenTimeAuthorization {
+    private(set) var status: ScreenTimeAuthorizationStatus
+    private(set) var lastRequestFailed = false
+    private let provider: AuthorizationProviding
+
+    init(provider: AuthorizationProviding) {
+        self.provider = provider
+        self.status = provider.currentStatus
+    }
+
+    func refresh() {
+        status = provider.currentStatus
+    }
+
+    func request() async {
+        do {
+            try await provider.requestAuthorization()
+            lastRequestFailed = false
+        } catch {
+            lastRequestFailed = true
+        }
+        refresh()
+    }
+}

Severed/Services/ShieldController.swift

@@ -0,0 +1,108 @@
+//
+//  ShieldController.swift
+//  Severed
+//
+
+import FamilyControls
+import Foundation
+import ManagedSettings
+
+/// Applies and clears app shields for rules. One implementation talks to
+/// ManagedSettings; the mock records calls for tests.
+protocol ShieldApplying: AnyObject {
+    func applyShield(ruleID: UUID, selectionData: Data?, mode: SelectionMode)
+    /// Clears every shield except those for the given rule IDs. Covers rules
+    /// that were deleted or expired while the app was not running.
+    func clearShields(except activeRuleIDs: Set<UUID>)
+}
+
+/// Real shield enforcement via per-rule `ManagedSettingsStore`s. Store names
+/// are tracked in UserDefaults because ManagedSettings cannot enumerate them.
+final class ManagedSettingsShieldController: ShieldApplying {
+    private static let trackedIDsKey = "shieldedRuleIDs"
+    private let defaults: UserDefaults
+
+    init(defaults: UserDefaults = .standard) {
+        self.defaults = defaults
+    }
+
+    func applyShield(ruleID: UUID, selectionData: Data?, mode: SelectionMode) {
+        let store = store(for: ruleID)
+        let selection = AppSelectionCodec.decode(selectionData)
+        switch mode {
+        case .block:
+            store.shield.applications =
+                selection.applicationTokens.isEmpty ? nil : selection.applicationTokens
+            store.shield.applicationCategories =
+                selection.categoryTokens.isEmpty ? nil : .specific(selection.categoryTokens)
+            store.shield.webDomains =
+                selection.webDomainTokens.isEmpty ? nil : selection.webDomainTokens
+        case .allowOnly:
+            store.shield.applicationCategories = .all(except: selection.applicationTokens)
+            store.shield.webDomainCategories = .all(except: selection.webDomainTokens)
+        }
+        track(ruleID: ruleID)
+    }
+
+    func clearShields(except activeRuleIDs: Set<UUID>) {
+        for ruleID in trackedIDs.subtracting(activeRuleIDs) {
+            store(for: ruleID).clearAllSettings()
+            untrack(ruleID: ruleID)
+        }
+    }
+
+    private func store(for ruleID: UUID) -> ManagedSettingsStore {
+        ManagedSettingsStore(named: ManagedSettingsStore.Name("rule-\(ruleID.uuidString)"))
+    }
+
+    private var trackedIDs: Set<UUID> {
+        Set((defaults.stringArray(forKey: Self.trackedIDsKey) ?? []).compactMap(UUID.init))
+    }
+
+    private func track(ruleID: UUID) {
+        let ids = trackedIDs.union([ruleID])
+        defaults.set(ids.map(\.uuidString).sorted(), forKey: Self.trackedIDsKey)
+    }
+
+    private func untrack(ruleID: UUID) {
+        let ids = trackedIDs.subtracting([ruleID])
+        defaults.set(ids.map(\.uuidString).sorted(), forKey: Self.trackedIDsKey)
+    }
+}
+
+/// Records shield operations without touching the system. Used by tests and
+/// UI-test launches.
+final class MockShieldController: ShieldApplying {
+    private(set) var shieldedRuleIDs: Set<UUID> = []
+    private(set) var appliedModes: [UUID: SelectionMode] = [:]
+
+    func applyShield(ruleID: UUID, selectionData: Data?, mode: SelectionMode) {
+        shieldedRuleIDs.insert(ruleID)
+        appliedModes[ruleID] = mode
+    }
+
+    func clearShields(except activeRuleIDs: Set<UUID>) {
+        shieldedRuleIDs.formIntersection(activeRuleIDs)
+        appliedModes = appliedModes.filter { activeRuleIDs.contains($0.key) }
+    }
+}
+
+/// Encodes/decodes `FamilyActivitySelection` for persistence on the rule model.
+enum AppSelectionCodec {
+    static func encode(_ selection: FamilyActivitySelection) -> Data? {
+        try? JSONEncoder().encode(selection)
+    }
+
+    static func decode(_ data: Data?) -> FamilyActivitySelection {
+        guard let data,
+              let selection = try? JSONDecoder().decode(FamilyActivitySelection.self, from: data)
+        else { return FamilyActivitySelection() }
+        return selection
+    }
+
+    static func count(of selection: FamilyActivitySelection) -> Int {
+        selection.applicationTokens.count
+            + selection.categoryTokens.count
+            + selection.webDomainTokens.count
+    }
+}