lotus(#4): pin camera into spotlight during screenshare (A5)

Review found the manual pin only chose among cameras when no screenshare
was active; during a screenshare the screenshare won the spotlight and the
pinned camera was demoted to an ignored PiP. Apply the override at the
spotlightAndPip$ level: when a pin is explicitly set, surface that camera
in the spotlight alongside the shared screen. No manual pin = unchanged.

Note: a pin persists if the pinned user briefly leaves and rejoins; the
host clears it via focus_participant{userId:null} (by design).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/state/CallViewModel/CallViewModel.ts

@@ -1011,7 +1011,22 @@ export function createCallViewModel$(
         return screenShares$.pipe(
           switchMap((screenShares) => {
             if (screenShares.length > 0)
-              return of({ spotlight: screenShares, pip$: spotlightSpeaker$ });
+              // [lotus #4/A5] During a screenshare, if the host has explicitly
+              // pinned a participant, surface that camera in the spotlight
+              // alongside the shared screen (the whole point of "focus camera
+              // during screenshare"). With no manual pin this is unchanged:
+              // the screenshare alone is spotlighted.
+              return combineLatest([manualSpotlightUserId$, userMedia$]).pipe(
+                map(([manualUserId, mediaItems]) => {
+                  const pinned =
+                    manualUserId !== null
+                      ? mediaItems.find((m) => m.userId === manualUserId)
+                      : undefined;
+                  return pinned
+                    ? { spotlight: [...screenShares, pinned], pip$: of(undefined) }
+                    : { spotlight: screenShares, pip$: spotlightSpeaker$ };
+                }),
+              );
 
             return spotlightSpeaker$.pipe(
               map((speaker) => ({