feat(apple/M1+M3+M4): widgets, Live Activity, and Siri/Shortcuts intents

The extension-side + App Intents surface for design/apple-live-activities-and-
widgets.md. The iOS-framework code (WidgetKit/ActivityKit/AppIntents) can't be
compiled by the macOS `swift build` CI target and needs the Xcode widget-
extension target that only exists once created in the GUI — see the checklist in
the memory note. What macOS DID verify: HostEntity (AppIntents is available on
macOS), the shared attribute/notification plumbing, and that nothing regressed
(142 tests green).

Shared (PunktfunkShared):
- PunktfunkSessionAttributes (ActivityAttributes) — the one type app + extension
  share; gated os(iOS) (ActivityKit imports on macOS but its types are
  unavailable, so canImport would wrongly admit it).
- EndStreamIntent (LiveActivityIntent) — posts .punktfunkEndActiveSession.
- HostEntity + HostEntityQuery (AppEntity over the shared store) — the intent /
  widget-config parameter type; canImport(AppIntents), so macOS type-checks it.
- New notifications: end-active-session, open-deep-link.

M1 widget extension sources (Sources/PunktfunkWidgets/, NOT a SwiftPM target —
`swift build` ignores the dir):
- PunktfunkWidgetBundle (@main): HostsWidget + PunktfunkSessionLiveActivity.
- HostsWidget (kind "PunktfunkHosts"): reads the shared-suite store, sorts by
  recency, deep-links each host; small/medium/accessory families; empty state.
- SessionLiveActivity: Lock-Screen banner + Dynamic Island (elapsed timer,
  mode line, background countdown, End button).

M3 controller (app, iOS): SessionActivityController owns the Activity lifecycle
(request/update/end + launch orphan-sweep + staleDate); ContentView drives it
from the model's phase/isBackgrounded/backgroundDeadline (which SessionModel now
publishes), keeping ActivityKit out of the cross-platform model.

M4 (app, iOS): ConnectToHost/WakeHost intents + AppShortcutsProvider; Connect
routes via .punktfunkOpenDeepLink into the same onOpenURL router (one set of
guards); Wake reuses the WoL path; End surfaced to Shortcuts too.

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

clients/apple/Sources/PunktfunkShared/HostEntity.swift

@@ -0,0 +1,56 @@
+// The saved-host as an App Intents entity — the parameter type for the Connect/Wake intents and
+// the configurable single-host widget. Lives in the shared module (not the app) because widget
+// *configuration* intents execute in the EXTENSION process, so the entity can't be app-only.
+//
+// AppIntents is genuinely available on macOS (13+), so this is gated on `canImport(AppIntents)`
+// (unlike ActivityKit, whose macOS types are unavailable) — it compiles on every platform and the
+// entity query reads the same shared App-Group store the widget does.
+
+#if canImport(AppIntents)
+import AppIntents
+import Foundation
+
+public struct HostEntity: AppEntity, Identifiable {
+    public static let typeDisplayRepresentation = TypeDisplayRepresentation(name: "Host")
+    public static let defaultQuery = HostEntityQuery()
+
+    public let id: UUID
+    public let name: String
+
+    public init(id: UUID, name: String) {
+        self.id = id
+        self.name = name
+    }
+
+    public init(_ host: StoredHost) {
+        self.id = host.id
+        self.name = host.displayName
+    }
+
+    public var displayRepresentation: DisplayRepresentation {
+        DisplayRepresentation(title: "\(name)")
+    }
+}
+
+public struct HostEntityQuery: EntityQuery {
+    public init() {}
+
+    public func entities(for identifiers: [UUID]) async throws -> [HostEntity] {
+        Self.loadHosts().filter { identifiers.contains($0.id) }.map(HostEntity.init)
+    }
+
+    /// Sorted most-recent first — Siri/Shortcuts and the widget config picker suggest recent hosts.
+    public func suggestedEntities() async throws -> [HostEntity] {
+        Self.loadHosts().map(HostEntity.init)
+    }
+
+    static func loadHosts() -> [StoredHost] {
+        guard let data = AppGroup.defaults.data(forKey: DefaultsKey.hosts),
+              let hosts = try? JSONDecoder().decode([StoredHost].self, from: data)
+        else { return [] }
+        return hosts.sorted {
+            ($0.lastConnected ?? .distantPast) > ($1.lastConnected ?? .distantPast)
+        }
+    }
+}
+#endif