fix(app): rebase onto main, re-home debug-mode watchdog into the #312 quit drain

Rebases wave-1-debug-diag onto origin/main now that #310-#316 merged
(#312's quit-path restructuring in particular). Structural follow-up:

- The debug-logging-mode watchdog (debug_mode.rs) previously used the
  detached memlog.rs pattern (no shutdown tracking). #312 replaced the
  old shutdown_orchestrators() with a proper ShutdownHandles/
  drain_shutdown_handles structure that every other periodic background
  task (updater, telemetry, iostat, and now #311's bottleneck sampler)
  registers into for a no-orphan quit drain. Re-homed the watchdog into
  that same structure: a new DebugModeRuntime (task + shutdown watch,
  no shared hub - the watchdog only reads/writes settings directly)
  on AppState, set_debug_mode_task/shutdown_debug_mode_task mirroring
  set_bottleneck_task/shutdown_bottleneck_task exactly, a debug_mode
  field on ShutdownHandles, and spawn_watchdog now runs the same
  select!-on-shutdown-or-tick loop bottleneck_hub/iostat_hub use
  instead of a bare loop.
- Added app_state::tests::debug_mode_runtime_task_and_shutdown_round_trip,
  mirroring bottleneck's round-trip test.
- privacy.png (light+dark) and 9 shell.spec.ts baselines (light+dark)
  regenerated via `just visual-update` (Docker) - the shell baselines
  drifted independently of this PR's own diff (same delta across every
  scenario in both themes), consistent with normal headless-Chromium
  rendering drift between visual-update runs; all 106 visual specs pass
  against the regenerated set.

No other conflicts: README.md, dtos.rs, settings.rs's redaction code,
en-US.json, Activity.vue, and fixtures.ts all auto-merged cleanly with
#311's bottleneck-tile additions coexisting alongside this PR's debug
logging toggle and diagnostic-bundle changes.

Verified after rebase: cargo test -p driven-app --lib (494 passed),
cargo clippy --workspace --all-targets -- -D warnings (clean),
cargo fmt --all --check (clean), pnpm lint (0 errors), pnpm format:check
(clean), pnpm test:unit (861 passed, 64 files), pnpm build / vue-tsc
(clean).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019xKUm9vH4ifb5LHR5szy1v

Author: pmaxhogan

src-tauri/src/app_state.rs

@@ -309,7 +309,7 @@ pub struct AppState {
     /// sampling runtime (the Activity dashboard's Bottleneck stat tile).
     bottleneck: BottleneckRuntime,
     /// issue #309: the debug-logging-mode 24h auto-off watchdog's task handle
-    /// + shutdown signal, so the app-quit drain joins it with no orphan
+    /// and shutdown signal, so the app-quit drain joins it with no orphan
     /// (mirrors [`UpdaterRuntime`]/[`IostatRuntime`]). No shared "hub" field
     /// like those two - the watchdog only reads/writes the persisted settings
     /// KV directly, nothing else on `AppState` needs to observe it.
@@ -2180,6 +2180,43 @@ pub(crate) mod tests {
         let _ = std::fs::remove_dir_all(dir);
     }
 
+    #[tokio::test]
+    async fn debug_mode_runtime_task_and_shutdown_round_trip() {
+        // Issue #309: the debug-logging-mode watchdog's runtime bookkeeping.
+        // No hub getter to cover (unlike bottleneck/iostat) - just the
+        // set/shutdown task pair, mirrors
+        // `bottleneck_runtime_hub_task_and_shutdown_round_trip`.
+        let (state, dir) = temp_state().await;
+        let app_state = AppState::new(
+            state,
+            HashMap::new(),
+            RemoteMode::Fake,
+            default_fake_registry(),
+        );
+
+        // No task registered yet: shutdown is a safe no-op.
+        assert!(app_state.shutdown_debug_mode_task().is_none());
+
+        // Register a task that exits promptly on the shutdown signal (the
+        // real watchdog's own shape), then confirm shutdown signals + hands
+        // back the handle so the quit drain can join it.
+        let (shutdown_tx, mut shutdown_rx) = watch::channel(false);
+        let task = tokio::spawn(async move {
+            let _ = shutdown_rx.changed().await;
+        });
+        app_state.set_debug_mode_task(task, shutdown_tx);
+
+        let handle = app_state
+            .shutdown_debug_mode_task()
+            .expect("the just-registered task round-trips");
+        handle.await.unwrap();
+
+        // Taken: a second shutdown call is again a safe no-op.
+        assert!(app_state.shutdown_debug_mode_task().is_none());
+
+        let _ = std::fs::remove_dir_all(dir);
+    }
+
     #[tokio::test]
     async fn vss_helper_manager_installs_and_shutdown_is_noop() {
         // Issue #25: AppState owns the least-privilege VSS helper broker manager -