iOS: Siri and Shortcuts, and a widget (#427, #428)

Siri: App Intents with phrases that need no setup: Resume, Pause,
Skip forward, Skip back, Set a sleep timer, How many unread. The
playback ones are AudioPlaybackIntents, run in the app and allowed to
start audio from the background. Playback is now one shared instance
(Playback.shared) so Siri and the widget reach it with no page loaded.
It remembers the last episode and its place (LastPlayed), so Resume
works with the app closed; the page, opened afterwards, does not know
about an episode started that way.

Widget: small and medium on the home screen, circular and rectangular
on the lock screen. It shows the unread count and the last episode,
with a Resume or Pause button (PlayPauseIntent, shared with Siri). It
draws what the app writes to the App Group group.net.sdf1.ipx. The app
asks for a redraw on play, pause, a new episode or a new count, not on
every position, since iOS rations redraws. Shared/ builds into both
targets, with WIDGET set in the widget's, where the player does not
exist.

ipx's push now carries content-available, which wakes the closed app
for a moment to give the widget the count the icon just got (#433).

Tested: unit tests for the snapshot and the remembered place, 19 in
all; in the simulator, playing an episode wrote the snapshot to the
App Group. Not testable there: Siri, and the widget drawn.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ios/Sources/Intents.swift

@@ -0,0 +1,109 @@
+import AppIntents
+
+// Siri and Shortcuts (#427). Each is an App Intent, and IPXShortcuts below gives the common ones
+// phrases that work with nothing set up: "Resume iPX", "Pause iPX", "How many unread in iPX".
+// The playback ones are AudioPlaybackIntents, which iOS runs in the app and lets start audio
+// from the background, so they work with the phone locked and the app closed.
+
+struct ResumeIntent: AudioPlaybackIntent {
+    static let title: LocalizedStringResource = "Resume Listening"
+    static let description = IntentDescription(
+        "Carries on with what iPX was playing, or the last episode, from where you left off.")
+
+    @MainActor
+    func perform() async throws -> some IntentResult {
+        guard Playback.shared.resumeLast() else { throw NothingToResume() }
+        return .result()
+    }
+}
+
+/// What Siri says when there is no episode to carry on with.
+struct NothingToResume: Error, CustomLocalizedStringResourceConvertible {
+    var localizedStringResource: LocalizedStringResource {
+        "There is nothing to resume. Play an episode in iPX first."
+    }
+}
+
+struct PauseIntent: AudioPlaybackIntent {
+    static let title: LocalizedStringResource = "Pause"
+    static let description = IntentDescription("Pauses what iPX is playing.")
+
+    @MainActor
+    func perform() async throws -> some IntentResult {
+        Playback.shared.pause()
+        return .result()
+    }
+}
+
+struct SkipForwardIntent: AudioPlaybackIntent {
+    static let title: LocalizedStringResource = "Skip Forward"
+    static let description = IntentDescription("Skips 30 seconds ahead, as the player's button does.")
+
+    @MainActor
+    func perform() async throws -> some IntentResult {
+        Playback.shared.seek(to: Playback.shared.currentTime + 30)
+        return .result()
+    }
+}
+
+struct SkipBackIntent: AudioPlaybackIntent {
+    static let title: LocalizedStringResource = "Skip Back"
+    static let description = IntentDescription("Goes back 15 seconds, as the player's button does.")
+
+    @MainActor
+    func perform() async throws -> some IntentResult {
+        Playback.shared.seek(to: Playback.shared.currentTime - 15)
+        return .result()
+    }
+}
+
+struct SleepTimerIntent: AudioPlaybackIntent {
+    static let title: LocalizedStringResource = "Set Sleep Timer"
+    static let description = IntentDescription(
+        "Pauses iPX after a number of minutes, fading out over the last ten seconds. Zero turns it off.")
+
+    @Parameter(title: "Minutes", default: 30, inclusiveRange: (0, 600),
+               requestValueDialog: "For how many minutes?")
+    var minutes: Int
+
+    @MainActor
+    func perform() async throws -> some IntentResult & ProvidesDialog {
+        Playback.shared.sleep(after: Double(minutes) * 60)
+        return .result(dialog: minutes == 0 ? "The sleep timer is off." : "iPX will pause in \(minutes) minutes.")
+    }
+}
+
+struct UnreadIntent: AppIntent {
+    static let title: LocalizedStringResource = "Unread Count"
+    static let description = IntentDescription("How many items are unread in All Subscriptions.")
+
+    func perform() async throws -> some IntentResult & ReturnsValue<Int> & ProvidesDialog {
+        guard let n = await Badge.fetch() else {
+            return .result(value: 0, dialog: "iPX could not reach your server.")
+        }
+        await MainActor.run { Badge.set(n) }
+        return .result(value: n, dialog: n == 0 ? "Nothing is unread." : "\(n) unread in All Subscriptions.")
+    }
+}
+
+struct IPXShortcuts: AppShortcutsProvider {
+    static var appShortcuts: [AppShortcut] {
+        AppShortcut(intent: ResumeIntent(),
+                    phrases: ["Resume \(.applicationName)", "Play \(.applicationName)",
+                              "Carry on listening in \(.applicationName)"],
+                    shortTitle: "Resume", systemImageName: "play.fill")
+        AppShortcut(intent: PauseIntent(), phrases: ["Pause \(.applicationName)"],
+                    shortTitle: "Pause", systemImageName: "pause.fill")
+        AppShortcut(intent: SkipForwardIntent(),
+                    phrases: ["Skip forward in \(.applicationName)", "Skip ahead in \(.applicationName)"],
+                    shortTitle: "Skip Forward", systemImageName: "goforward.30")
+        AppShortcut(intent: SkipBackIntent(), phrases: ["Skip back in \(.applicationName)"],
+                    shortTitle: "Skip Back", systemImageName: "gobackward.15")
+        AppShortcut(intent: SleepTimerIntent(),
+                    phrases: ["Set a sleep timer in \(.applicationName)", "\(.applicationName) sleep timer"],
+                    shortTitle: "Sleep Timer", systemImageName: "moon.zzz")
+        AppShortcut(intent: UnreadIntent(),
+                    phrases: ["How many unread in \(.applicationName)", "What's new in \(.applicationName)"],
+                    shortTitle: "Unread", systemImageName: "tray.full")
+    }
+}