feat(ui): focus trap for consent dialog + recording-state live region (T7.5, FR-UX-4)

Traps focus in the recording-consent overlay the same way as Settings.
Adds a visually-hidden aria-live region announcing "Recording
started/paused/stopped" — previously nothing in the header was a live
region, so a non-visual user had no way to learn recording had begun.

src/App.svelte

@@ -7,6 +7,7 @@
   import Settings from "./lib/views/Settings.svelte";
   import ConsentNotice from "./lib/components/ConsentNotice.svelte";
   import LevelMeter from "./lib/components/LevelMeter.svelte";
+  import { trapFocus } from "./lib/actions/trapFocus";
   import { recording } from "./lib/stores/recording.svelte";
   import { settings } from "./lib/stores/settings.svelte";
   import { meetings } from "./lib/stores/meetings.svelte";
@@ -64,6 +65,23 @@
     );
   }
 
+  // Screen-reader announcement for recording state changes (T7.5, FR-UX-4) —
+  // nothing else in the header is a live region, so this is the only way a
+  // non-visual user learns recording started/stopped. Tracked via an effect
+  // (not a plain $derived) so "stopped" fires only after having recorded,
+  // never on initial idle load.
+  let recordingAnnouncement = $state("");
+  let previousRecordingState = recording.state;
+  $effect(() => {
+    const current = recording.state;
+    if (current !== previousRecordingState) {
+      if (current === "recording") recordingAnnouncement = "Recording started";
+      else if (current === "paused") recordingAnnouncement = "Recording paused";
+      else if (previousRecordingState !== "idle") recordingAnnouncement = "Recording stopped";
+      previousRecordingState = current;
+    }
+  });
+
   function onGlobalKeydown(e: KeyboardEvent) {
     if (e.key === "Escape") {
       if (showConsent) showConsent = false;
@@ -100,6 +118,7 @@
 </script>
 
 <div class="app" data-theme={resolvedTheme}>
+  <div class="sr-only" role="status" aria-live="polite">{recordingAnnouncement}</div>
   <header class="bar">
     <strong>WhispAssist</strong>
     <span class="muted">local · private</span>
@@ -152,7 +171,14 @@
   </header>
 
   {#if showConsent}
-    <div class="consent-overlay" role="dialog" aria-modal="true" aria-label="Recording consent">
+    <div
+      class="consent-overlay"
+      role="dialog"
+      aria-modal="true"
+      aria-label="Recording consent"
+      tabindex="-1"
+      use:trapFocus
+    >
       <ConsentNotice onAccept={acceptConsentAndRecord} onCancel={() => (showConsent = false)} />
     </div>
   {/if}
@@ -169,6 +195,17 @@
 </div>
 
 <style>
+  .sr-only {
+    position: absolute;
+    width: 1px;
+    height: 1px;
+    padding: 0;
+    margin: -1px;
+    overflow: hidden;
+    clip: rect(0, 0, 0, 0);
+    white-space: nowrap;
+    border: 0;
+  }
   :global(:root) {
     --bg: #ffffff;
     --fg: #1a1a1a;