fix: avoid creating persistent phantom atom for empty-string key when cwd is null

When useGitStatus(null) was called, gitStatusStateAtom('') was evaluated,
permanently registering '' in knownGitStatusCwds and creating a keepAlive
atom that was never garbage collected. Use a static sentinel atom for the
null case to avoid touching the atom family entirely.

Author: cursoragent

apps/web/src/lib/gitStatusState.ts

@@ -30,6 +30,10 @@ const EMPTY_GIT_STATUS_STATE = Object.freeze<GitStatusState>({
   isPending: false,
 });
 
+const EMPTY_GIT_STATUS_ATOM = Atom.make(EMPTY_GIT_STATUS_STATE).pipe(
+  Atom.keepAlive,
+  Atom.withLabel("git-status:null"),
+);
 const NOOP: () => void = () => undefined;
 const watchedGitStatuses = new Map<string, WatchedGitStatus>();
 const knownGitStatusCwds = new Set<string>();
@@ -126,7 +130,7 @@ export function resetGitStatusStateForTests(): void {
 export function useGitStatus(cwd: string | null): GitStatusState {
   useEffect(() => watchGitStatus(cwd), [cwd]);
 
-  const state = useAtomValue(gitStatusStateAtom(cwd ?? ""));
+  const state = useAtomValue(cwd !== null ? gitStatusStateAtom(cwd) : EMPTY_GIT_STATUS_ATOM);
   return cwd === null ? EMPTY_GIT_STATUS_STATE : state;
 }