perf(meeting): only run process poller while auto-capture is enabled

Previously the 15-second meeting-detection setInterval was started in
onMount unconditionally (when Tauri runtime was available). When
`settings.meetingAutoCapture` was disabled the callback still fired every
15 s, just to early-return — burning a wakeup that did no useful work
and confusing "is this firing? did the toggle take effect?" debugging.

Move the timer into a `$effect` whose only tracked dependency is
`settings.meetingAutoCapture`. Toggling off now clears the interval; toggling
on creates a fresh one. Reads of `meetingAutoCaptureApps` and `globalHotkey`
happen inside the interval callback (post-setup) so they don't trigger the
effect to tear down on every keystroke in the apps editor.

The `meetingCapturePoller` variable and its `onDestroy` cleanup are gone —
the effect's own cleanup return takes care of it on unmount.

https://claude.ai/code/session_0189xUb6ie6t9qHkzatGZ9Rb

src/routes/+layout.svelte

@@ -340,43 +340,52 @@
       invoke("prewarm_default_model_cmd").catch(() => {});
     }
 
-    // Meeting auto-capture: poll the process list and toast when a match
+    // Meeting auto-capture is wired up below as a `$effect` so the
-    // appears (edge-triggered — no repeat toasts until the app goes away
+    // 15-second poller only exists while the setting is enabled —
-    // and comes back). We never start recording from this signal; the
+    // toggling off in Settings stops the wakeups, not just the work.
-    // user decides whether to hit the hotkey.
-    if (tauriRuntimeAvailable) {
-      let previous: Set<string> = new Set();
-      meetingCapturePoller = window.setInterval(async () => {
-        if (!settings.meetingAutoCapture) { previous = new Set(); return; }
-        const patterns = settings.meetingAutoCaptureApps;
-        if (!Array.isArray(patterns) || patterns.length === 0) return;
-        try {
-          const matches: string[] = await invoke("detect_meeting_processes", { patterns });
-          const current = new Set(matches);
-          for (const match of matches) {
-            if (!previous.has(match)) {
-              toasts.info(
-                `${match[0].toUpperCase()}${match.slice(1)} detected`,
-                `Press ${settings.globalHotkey} to start recording.`,
-              );
-            }
-          }
-          previous = current;
-        } catch { /* ignore — backend may be mid-restart */ }
-      }, 15000);
-    }
   });
 
-  let meetingCapturePoller: number | null = null;
+  // Meeting auto-capture poller. Edge-triggered: the first time a matching
+  // process appears we surface a non-modal toast; subsequent ticks where
+  // the same match is still present stay quiet until the app exits and
+  // returns. We never start recording from this signal — the user decides.
+  //
+  // The effect's only tracked dependencies are `tauriRuntimeAvailable`
+  // (constant after mount) and `settings.meetingAutoCapture`. Reads of
+  // `settings.meetingAutoCaptureApps` and `settings.globalHotkey` happen
+  // inside the interval callback, which runs after the synchronous setup
+  // and therefore is not tracked — editing the apps list doesn't tear
+  // down the poller.
+  $effect(() => {
+    if (!tauriRuntimeAvailable) return;
+    if (!settings.meetingAutoCapture) return;
+
+    let previous: Set<string> = new Set();
+    const id = window.setInterval(async () => {
+      const patterns = settings.meetingAutoCaptureApps;
+      if (!Array.isArray(patterns) || patterns.length === 0) return;
+      try {
+        const matches: string[] = await invoke("detect_meeting_processes", { patterns });
+        const current = new Set(matches);
+        for (const match of matches) {
+          if (!previous.has(match)) {
+            toasts.info(
+              `${match[0].toUpperCase()}${match.slice(1)} detected`,
+              `Press ${settings.globalHotkey} to start recording.`,
+            );
+          }
+        }
+        previous = current;
+      } catch { /* ignore — backend may be mid-restart */ }
+    }, 15000);
+
+    return () => { window.clearInterval(id); };
+  });
 
   onDestroy(() => {
     window.removeEventListener("resize", handleResize);
     if (onWindowError) window.removeEventListener("error", onWindowError);
     if (onUnhandledRejection) window.removeEventListener("unhandledrejection", onUnhandledRejection);
-    if (meetingCapturePoller !== null) {
-      window.clearInterval(meetingCapturePoller);
-      meetingCapturePoller = null;
-    }
     if (!tauriRuntimeAvailable) {
       return;
     }