feat(flow): harden host handoff, session UX, and Live Activity brand

- fix(keyboard): drop unusable extensionContext.open; report the real
  result of UIApplication.open and cancel the start watchdog immediately
  on failure with clear "open OSGKeyboard" guidance instead of a 30s spin
- feat(capture): recover from audio route changes (AirPods/wired headset
  plug-unplug) and phone-call interruptions by rebuilding the engine/tap
  against the live hardware format
- feat(home): add a "Start" button in the Home footer when a session is
  inactive and permissions are granted (no-jump manual restart)
- feat(hostapps): expand the return whitelist to 46 apps (Signal, Zoom,
  Instagram, X, Douyin, Zhihu, Bilibili, Things, Firefox, ...) with
  en/zh-Hans names and synced LSApplicationQueriesSchemes
- feat(island): use a "ready" checkmark instead of a mic glyph while idle
  and set a staleDate so an orphaned Live Activity fades after a force-quit
- feat(coldstart): use the template OSG brand mark instead of a system
  waveform glyph in the cold-start overlay
- perf(keyboard): rely on Darwin notifications as the primary session
  signal and drop the fallback poll from 1s to 3s
- fix(keyboard): remove the redundant "Start" text button next to the
  inactive-session hint on the keyboard
- docs: correct the per-take cap to 210s (3.5 min) and document that
  force-quitting no longer resurrects the session (tracker + READMEs)

OSGKeyboardExt/Views/KeyboardRootView.swift

@@ -142,8 +142,7 @@ public struct KeyboardRootView: View {
                 micDisabled: state.micDisabled,
                 micDisabledHint: state.micDisabledHint,
                 cursorDragHintActive: state.cursorDragActive,
-                openSettings: state.openSettings,
-                startFlowSession: state.startFlowSession
+                openSettings: state.openSettings
             )
             .frame(height: KeyboardLayoutMetrics.transcriptLineHeight)
         }
@@ -336,7 +335,6 @@ private struct TranscriptLine: View {
     let micDisabledHint: String
     let cursorDragHintActive: Bool
     let openSettings: () -> Void
-    let startFlowSession: () -> Void
 
     var body: some View {
         ZStack {
@@ -366,18 +364,9 @@ private struct TranscriptLine: View {
                         .font(TypeStyle.caption)
                         .foregroundStyle(palette.textTertiary)
                 } else {
-                    HStack(spacing: 6) {
-                        ExtL10n.text("keyboard.flow.sessionInactive")
-                            .font(TypeStyle.caption)
-                            .foregroundStyle(palette.textTertiary)
-                        Button(action: startFlowSession) {
-                            ExtL10n.text("keyboard.flow.start")
-                                .font(TypeStyle.caption)
-                                .foregroundStyle(palette.accent)
-                        }
-                        .buttonStyle(.plain)
-                        .accessibilityHint(ExtL10n.text("keyboard.flow.startA11y"))
-                    }
+                    ExtL10n.text("keyboard.flow.sessionInactive")
+                        .font(TypeStyle.caption)
+                        .foregroundStyle(palette.textTertiary)
                 }
             case .requestingPermissions:
                 HStack(spacing: 6) {