feat(focus-timer): integrate with float window + add pop-out button

Jake's feedback on Phase 1: make the timer pinnable / always-on-top,
combined with the existing Now-list pop-out. Two changes:

1. Mount <FocusTimer /> in src/routes/float/+layout@.svelte so the
   running countdown stays visible in the always-on-top float window
   alongside the WIP task list. No content change to the float page
   itself — the timer is a global overlay.

2. Add a pop-out icon to the main-window focus timer that opens the
   existing /float route via window.open. One click → timer + Now
   list pinned on top without touching main window focus. Hidden
   inside the float window itself (detected via URL) so you cannot
   recursively pop out.

Result matches the Todo float-out UX the user already knows:
click ExternalLink, you get a small always-on-top window with
tasks + a live countdown ring in the top-right.

src/lib/components/FocusTimer.svelte

@@ -15,8 +15,26 @@
   // follows the sensory-zone theme switcher in Settings.
 
   import { onMount, onDestroy } from "svelte";
-  import { X, Plus } from "lucide-svelte";
+  import { X, Plus, ExternalLink } from "lucide-svelte";
   import { focusTimer } from "$lib/stores/focusTimer.svelte.js";
+  import { hasTauriRuntime } from "$lib/utils/runtime.js";
+
+  // Hide the "pop out" button inside the float window itself — opening
+  // a second float from a float would be silly and would re-mount the
+  // same component. Detect via URL rather than a prop so we do not
+  // have to thread context through every mount site.
+  let isSecondaryWindow = $state(false);
+  if (typeof window !== "undefined") {
+    isSecondaryWindow = window.location.pathname.startsWith("/float")
+      || window.location.pathname.startsWith("/viewer");
+  }
+
+  function handlePopOut() {
+    // Mirror the button in TasksPage.svelte — opens the always-on-top
+    // Now list + pinned timer in one floating window.
+    if (!hasTauriRuntime()) return;
+    window.open("/float", "_blank", "width=380,height=520");
+  }
 
   const RING_SIZE = 64;
   const RING_STROKE = 5;
@@ -148,6 +166,16 @@
         >
           <Plus size={14} aria-hidden="true" />
         </button>
+        {#if !isSecondaryWindow}
+          <button
+            class="icon-btn"
+            onclick={handlePopOut}
+            aria-label="Pop out timer + Now list into floating window"
+            title="Pop out (keeps timer + tasks on top)"
+          >
+            <ExternalLink size={14} aria-hidden="true" />
+          </button>
+        {/if}
         <button
           class="icon-btn"
           onclick={handleCancel}

src/routes/float/+layout@.svelte

@@ -12,6 +12,7 @@
     PREFERENCES_CHANGED_EVENT,
   } from "$lib/stores/preferences.svelte.js";
   import Titlebar from "$lib/components/Titlebar.svelte";
+  import FocusTimer from "$lib/components/FocusTimer.svelte";
   import { loadOsInfo, isLinux } from "$lib/utils/osInfo.js";
 
   let { children } = $props();
@@ -90,3 +91,9 @@
     {@render children()}
   </div>
 </div>
+
+<!-- Focus timer also visible in the always-on-top float window so a
+     running countdown stays with the Now list. The component is a
+     global overlay (position: fixed) so it pins to the top-right of
+     this window independent of the Tasks content below. -->
+<FocusTimer />