a11y: Tasks 2-6 -- App shell, Titlebar, ToggleSwitch, Stepper, animate.ts

- Add skip-to-content link and dynamic document title (App.svelte)
- Wrap titlebar in header landmark, enlarge traffic lights to 44px (Titlebar.svelte)
- Enlarge toggle switch to 52x28, improve OFF knob contrast (ToggleSwitch.svelte)
- Enlarge stepper buttons to 36px, add keyboard hold-to-repeat (Stepper.svelte)
- Add keyboard feedback to pressable, focus glow to glowHover (animate.ts)

src/App.svelte

@@ -75,6 +75,17 @@
     });
   });
 
+  // WCAG 2.4.2: Document title reflects current view
+  $effect(() => {
+    const viewNames: Record<string, string> = {
+      dashboard: "Dashboard",
+      breakScreen: "Break",
+      settings: "Settings",
+      stats: "Statistics",
+    };
+    document.title = `Core Cooldown — ${viewNames[effectiveView] ?? "Dashboard"}`;
+  });
+
   // When fullscreen_mode is OFF, the separate break window handles breaks,
   // so the main window should keep showing whatever view it was on (dashboard).
   const effectiveView = $derived(
@@ -85,11 +96,13 @@
 </script>
 
 <main class="relative h-full bg-black">
+  <a href="#main-content" class="skip-link">Skip to content</a>
   {#if $config.background_blobs_enabled}
     <BackgroundBlobs accentColor={$config.accent_color} breakColor={$config.break_color} />
   {/if}
   <Titlebar />
   <div
+    id="main-content"
     class="relative h-full overflow-hidden origin-top-left"
     style="
       transform: scale({zoomScale});