fix: show a generic "App Blocked" shield instead of mis-attributing a rule

The shield titled itself with the first enabled rule whose selection
contained the app, regardless of whether that rule was the one actually
blocking. When several rules covered the same app (e.g. a dormant
schedule + the active limit) it named the wrong rule.

Drop the rule-name lookup entirely: every shield now carries a generic
"App Blocked" title. Open-limit shields keep their functional detail
(running count + "Open (N left)" button) beneath that title. The
text-only decision moves into a pure, unit-tested ShieldPresentation in
Shared/, and the now-dead ShieldLookup.snapshot(containingApplication:)
is removed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

OpenAppLockTests/ShieldPresentationTests.swift

@@ -0,0 +1,53 @@
+//
+//  ShieldPresentationTests.swift
+//  OpenAppLockTests
+//
+
+import Testing
+
+@testable import OpenAppLock
+
+@Suite("Shield presentation")
+struct ShieldPresentationTests {
+    @Test("Fully-blocked shield is generic and names no rule")
+    func blockedIsGeneric() {
+        let presentation = ShieldPresentation.blocked
+        #expect(presentation.title == "App Blocked")
+        #expect(presentation.subtitle == "This app is blocked by OpenAppLock.")
+        #expect(presentation.secondaryButton == nil)
+    }
+
+    @Test("Open-limit shield with opens remaining shows counts and an Open button")
+    func openLimitWithOpensRemaining() {
+        let presentation = ShieldPresentation.openLimit(
+            opensUsed: 2, maxOpens: 5, sessionMinutes: 15)
+        // Title is generic — never the rule name.
+        #expect(presentation.title == "App Blocked")
+        #expect(presentation.subtitle.contains("Opened 2 of 5 times today"))
+        #expect(presentation.subtitle.contains("15 minutes"))
+        #expect(presentation.secondaryButton == "Open (3 left)")
+    }
+
+    @Test("A single remaining open reads in the singular")
+    func openLimitSingularRemaining() {
+        let presentation = ShieldPresentation.openLimit(
+            opensUsed: 4, maxOpens: 5, sessionMinutes: 15)
+        #expect(presentation.secondaryButton == "Open (1 left)")
+    }
+
+    @Test("Spent open-limit shield drops the Open button and reads as blocked")
+    func openLimitExhausted() {
+        let presentation = ShieldPresentation.openLimit(
+            opensUsed: 5, maxOpens: 5, sessionMinutes: 15)
+        #expect(presentation.title == "App Blocked")
+        #expect(presentation.subtitle == "No opens left today — the block lifts tomorrow.")
+        #expect(presentation.secondaryButton == nil)
+    }
+
+    @Test("Over-spending never yields a negative or non-nil Open button")
+    func openLimitOverSpent() {
+        let presentation = ShieldPresentation.openLimit(
+            opensUsed: 9, maxOpens: 5, sessionMinutes: 15)
+        #expect(presentation.secondaryButton == nil)
+    }
+}