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/Logic/RulePolicy.swift

@@ -0,0 +1,65 @@
+//
+//  RulePolicy.swift
+//  Severed
+//
+
+import Foundation
+
+/// Gates every mutation of a rule. This is where Hard Mode is enforced:
+/// while a hard-mode rule is actively blocking, nothing about it can be
+/// weakened until the window ends.
+enum RulePolicy {
+    /// True while the rule is actively blocking with Hard Mode on.
+    static func isHardLocked(
+        _ rule: BlockingRule, at now: Date = .now, calendar: Calendar = .current
+    ) -> Bool {
+        rule.hardMode && rule.status(at: now, calendar: calendar).isActive
+    }
+
+    static func canEdit(
+        _ rule: BlockingRule, at now: Date = .now, calendar: Calendar = .current
+    ) -> Bool {
+        !isHardLocked(rule, at: now, calendar: calendar)
+    }
+
+    static func canDisable(
+        _ rule: BlockingRule, at now: Date = .now, calendar: Calendar = .current
+    ) -> Bool {
+        !isHardLocked(rule, at: now, calendar: calendar)
+    }
+
+    static func canDelete(
+        _ rule: BlockingRule, at now: Date = .now, calendar: Calendar = .current
+    ) -> Bool {
+        !isHardLocked(rule, at: now, calendar: calendar)
+    }
+
+    /// Whether the user may lift the current block early ("Unblock").
+    /// Requires an active window and Hard Mode off.
+    static func canUnblock(
+        _ rule: BlockingRule, at now: Date = .now, calendar: Calendar = .current
+    ) -> Bool {
+        rule.status(at: now, calendar: calendar).isActive && !rule.hardMode
+    }
+
+    /// Hard Mode can always be turned on, but never off while the rule is
+    /// actively blocking — that is the whole point of a hard block.
+    static func canTurnOffHardMode(
+        _ rule: BlockingRule, at now: Date = .now, calendar: Calendar = .current
+    ) -> Bool {
+        !isHardLocked(rule, at: now, calendar: calendar)
+    }
+
+    /// Pauses the rule's current window. Returns false (and changes nothing)
+    /// when unblocking is not allowed.
+    @discardableResult
+    static func unblock(
+        _ rule: BlockingRule, at now: Date = .now, calendar: Calendar = .current
+    ) -> Bool {
+        guard canUnblock(rule, at: now, calendar: calendar),
+              let window = rule.schedule.activeWindow(containing: now, calendar: calendar)
+        else { return false }
+        rule.pausedUntil = window.end
+        return true
+    }
+}

Severed/Logic/RuleSchedule.swift

@@ -0,0 +1,89 @@
+//
+//  RuleSchedule.swift
+//  Severed
+//
+
+import Foundation
+
+/// The recurring time window of a rule, independent of any persistence.
+///
+/// A window whose end is at or before its start crosses midnight: 22:00 → 06:00
+/// starts on an enabled day and ends the following morning. `start == end`
+/// means a full 24-hour window.
+struct RuleSchedule: Hashable, Sendable {
+    var startMinutes: Int
+    var endMinutes: Int
+    var days: Set<Weekday>
+
+    var crossesMidnight: Bool { endMinutes <= startMinutes }
+
+    var durationMinutes: Int {
+        crossesMidnight
+            ? RuleSchedule.minutesPerDay - startMinutes + endMinutes
+            : endMinutes - startMinutes
+    }
+
+    /// The window containing `date`, if the schedule is active at that moment.
+    ///
+    /// Checks today's window and, for midnight-crossing schedules, the window
+    /// that started yesterday. The day a window *starts* on is the day that
+    /// must be enabled.
+    func activeWindow(containing date: Date, calendar: Calendar = .current) -> DateInterval? {
+        for dayOffset in [0, -1] {
+            guard
+                let day = calendar.date(byAdding: .day, value: dayOffset, to: date),
+                let window = window(onDayContaining: day, calendar: calendar),
+                window.start <= date, date < window.end
+            else { continue }
+            return window
+        }
+        return nil
+    }
+
+    func isActive(at date: Date, calendar: Calendar = .current) -> Bool {
+        activeWindow(containing: date, calendar: calendar) != nil
+    }
+
+    /// The next moment the schedule will begin a window strictly after `date`.
+    func nextStart(after date: Date, calendar: Calendar = .current) -> Date? {
+        guard !days.isEmpty else { return nil }
+        for dayOffset in 0...7 {
+            guard
+                let day = calendar.date(byAdding: .day, value: dayOffset, to: date),
+                let window = window(onDayContaining: day, calendar: calendar),
+                window.start > date
+            else { continue }
+            return window.start
+        }
+        return nil
+    }
+
+    /// The window starting on the given day, or nil when that weekday is not enabled.
+    private func window(onDayContaining day: Date, calendar: Calendar) -> DateInterval? {
+        let dayStart = calendar.startOfDay(for: day)
+        guard
+            let weekday = Weekday(rawValue: calendar.component(.weekday, from: dayStart)),
+            days.contains(weekday),
+            let start = calendar.date(byAdding: .minute, value: startMinutes, to: dayStart),
+            let end = calendar.date(
+                byAdding: .minute, value: startMinutes + durationMinutes, to: dayStart
+            )
+        else { return nil }
+        return DateInterval(start: start, end: end)
+    }
+
+    private static let minutesPerDay = 24 * 60
+}
+
+extension RuleSchedule {
+    /// "09:00" style label for a minutes-from-midnight value, matching the reference UI.
+    static func timeLabel(forMinutes minutes: Int) -> String {
+        let clamped = ((minutes % (24 * 60)) + 24 * 60) % (24 * 60)
+        return String(format: "%02d:%02d", clamped / 60, clamped % 60)
+    }
+
+    /// "09:00 – 17:00" range label used by rule details and preset cards.
+    var timeRangeLabel: String {
+        "\(Self.timeLabel(forMinutes: startMinutes)) – \(Self.timeLabel(forMinutes: endMinutes))"
+    }
+}

Severed/Logic/RuleStatus.swift

@@ -0,0 +1,73 @@
+//
+//  RuleStatus.swift
+//  Severed
+//
+
+import Foundation
+
+/// The live state of a rule at a moment in time. Derived, never stored.
+enum RuleStatus: Equatable, Sendable {
+    case disabled
+    /// Enabled but no days selected, so it never fires.
+    case dormant
+    /// Currently blocking; ends at the associated date.
+    case active(until: Date)
+    /// The user unblocked the current window; blocking resumes at the next window.
+    case paused(until: Date)
+    case upcoming(startsAt: Date)
+
+    var isActive: Bool {
+        if case .active = self { return true }
+        return false
+    }
+
+    /// Short status label shown on rule cards and detail sheets:
+    /// "6h left", "Starts in 22h", "Paused", "Disabled".
+    func label(relativeTo now: Date) -> String {
+        switch self {
+        case .disabled: "Disabled"
+        case .dormant: "No days selected"
+        case .paused: "Paused"
+        case .active(let until): "\(Self.countdown(from: now, to: until)) left"
+        case .upcoming(let start): "Starts in \(Self.countdown(from: now, to: start))"
+        }
+    }
+
+    /// Compact countdown matching the reference app: minutes under an hour,
+    /// hours (rounded up) under two days, then days.
+    static func countdown(from now: Date, to target: Date) -> String {
+        let minutes = max(1, Int(ceil(target.timeIntervalSince(now) / 60)))
+        guard minutes >= 60 else { return "\(minutes)m" }
+        let hours = (minutes + 59) / 60
+        guard hours >= 48 else { return "\(hours)h" }
+        return "\(hours / 24)d"
+    }
+}
+
+extension BlockingRule {
+    /// Live status of this rule. Schedule rules derive it from their time window;
+    /// time/open-limit rules report upcoming based on their enabled days only
+    /// (their blocking is triggered by usage, not the clock).
+    func status(at now: Date = .now, calendar: Calendar = .current) -> RuleStatus {
+        guard isEnabled else { return .disabled }
+        guard !days.isEmpty else { return .dormant }
+
+        guard kind == .schedule else {
+            guard let next = schedule.nextStart(after: now, calendar: calendar) else {
+                return .dormant
+            }
+            return .upcoming(startsAt: next)
+        }
+
+        if let window = schedule.activeWindow(containing: now, calendar: calendar) {
+            if let pausedUntil, pausedUntil > now {
+                return .paused(until: min(pausedUntil, window.end))
+            }
+            return .active(until: window.end)
+        }
+        if let next = schedule.nextStart(after: now, calendar: calendar) {
+            return .upcoming(startsAt: next)
+        }
+        return .dormant
+    }
+}