fix/polish: wave 1+2 improvements across six features

B1 - GIF upload progress: spinner on GIF button + disabled state while
     fetch+upload is in flight; clears on success or error
B2 - PiP position persistence: drag end saves left/top to localStorage;
     entering PiP restores saved position (clamped to current viewport)
B3 - PiP snap-to-corner: double-click the PiP overlay snaps to nearest
     corner with a 180ms CSS transition; saves new position
B4 - Device sessions loading state: useOtherUserDevices now returns
     {status:'loading'|'error'|'success', devices} instead of bare
     array; UserDeviceSessions shows spinner while loading
B5 - Device sessions error state: catch in hook sets status:'error';
     panel shows warning icon + 'Could not load sessions' message
B6 - Screenshare fullscreen Safari guard: hide button when
     document.fullscreenEnabled is false (iOS Safari, some mobile)
B7 - Status save error: show critical-coloured error text below Save
     button when saveState.status === AsyncStatus.Error
B9 - Encrypted search coverage counter: 'X / Y cached' badge next to
     'Encrypted Rooms' heading using existing localResult fields
D2 - PiP screenshare spotlight: track auto-spotlight in a ref; release
     spotlight when screenshare ends while in PiP mode

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/features/room/RoomInput.tsx

@@ -299,6 +299,7 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
     const gifBtnRef = useRef<HTMLButtonElement>(null);
     const [hideStickerBtn, setHideStickerBtn] = useState(document.body.clientWidth < 500);
     const [gifError, setGifError] = React.useState<string | null>(null);
+    const [gifUploading, setGifUploading] = React.useState(false);
 
     const isComposing = useComposingCheck();
 
@@ -519,6 +520,7 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
 
     const handleGifSelect = useCallback(
       async (gifUrl: string, w: number, h: number) => {
+        setGifUploading(true);
         try {
           // Only fetch from trusted Giphy CDN domains
           const allowed = [
@@ -562,6 +564,8 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
           if (!alive()) return;
           setGifError('Failed to send GIF. Please try again.');
           setTimeout(() => setGifError(null), 4000);
+        } finally {
+          if (alive()) setGifUploading(false);
         }
       },
       [mx, roomId, alive],
@@ -840,22 +844,27 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
                         ref={gifBtnRef}
                         aria-label="Insert GIF"
                         aria-pressed={gifOpen}
-                        onClick={() => setGifOpen(!gifOpen)}
+                        onClick={() => !gifUploading && setGifOpen(!gifOpen)}
                         variant="SurfaceVariant"
                         size="300"
                         radii="300"
+                        disabled={gifUploading}
                       >
-                        <Text
-                          size="T200"
-                          style={{
-                            fontWeight: 800,
-                            fontSize: '11px',
-                            letterSpacing: '0.04em',
-                            lineHeight: 1,
-                          }}
-                        >
-                          GIF
-                        </Text>
+                        {gifUploading ? (
+                          <Spinner variant="Secondary" size="100" />
+                        ) : (
+                          <Text
+                            size="T200"
+                            style={{
+                              fontWeight: 800,
+                              fontSize: '11px',
+                              letterSpacing: '0.04em',
+                              lineHeight: 1,
+                            }}
+                          >
+                            GIF
+                          </Text>
+                        )}
                       </IconButton>
                     </PopOut>
                   )}