fix(desktop): guarantee out-of-bounds composer is reclamped on load

Re-clamp once more on the next frame after pop-out so layout (sidebar widths,
fonts) has settled, and treat a degenerate pre-layout bounds rect as "unknown"
(fall back to the window) so we never clamp the box into a collapsed area. Net:
anyone who loads in with a stranded position is pulled back on-screen and the
fix is persisted, even if the first measure was premature.

apps/desktop/src/app/chat/composer/index.tsx

@@ -543,9 +543,12 @@ export function ChatBar({
     syncComposerMetrics()
   }, [poppedOut, syncComposerMetrics])
 
-  // Keep the floating box on-screen: re-clamp (with the real measured size) when
-  // it pops out and whenever the window resizes — so a position persisted on a
-  // bigger/other monitor, or a shrunk window, can never strand it out of reach.
+  // Keep the floating box on-screen: re-clamp (with the real measured size +
+  // thread bounds) when it pops out and on every window resize — so a position
+  // persisted on a bigger/other monitor, a shrunk window, or now-wider sidebar
+  // can never strand it. The rAF pass re-clamps after layout settles (sidebar
+  // widths, fonts), so anyone loading in out of bounds is pulled back + saved
+  // even if the first measure was premature.
   useEffect(() => {
     if (!poppedOut) {
       return undefined
@@ -558,10 +561,14 @@ export function ChatBar({
     }
 
     reclamp(true)
+    const raf = requestAnimationFrame(() => reclamp(true))
     const onResize = () => reclamp(false)
     window.addEventListener('resize', onResize)
 
-    return () => window.removeEventListener('resize', onResize)
+    return () => {
+      cancelAnimationFrame(raf)
+      window.removeEventListener('resize', onResize)
+    }
   }, [poppedOut])
 
   useEffect(() => {

apps/desktop/src/store/composer-popout.ts

@@ -88,9 +88,11 @@ export function readPopoutBounds(composer: Element | null): PopoutBounds | undef
     return undefined
   }
 
-  const { bottom, left, right, top } = el.getBoundingClientRect()
+  const { bottom, height, left, right, top, width } = el.getBoundingClientRect()
 
-  return { bottom, left, right, top }
+  // Pre-layout (mount before first layout) the rect is empty — fall back to the
+  // window rather than clamping the box into a collapsed area.
+  return width > 0 && height > 0 ? { bottom, left, right, top } : undefined
 }
 
 // Bound the bottom/right inset so the WHOLE box stays inside `area` (the thread