stage-342: apply Opus SHOULD-FIX — tighten worktree status _run_git timeout 5s → 2s

Worst case 4×5s=20s per polling request on ThreadingHTTPServer pool is risky
given today's _cron_env_lock near-miss on production 8787. Status probes
should fail fast; client can retry. All four call sites use default timeout.

api/worktrees.py

@@ -13,7 +13,7 @@ import logging
 logger = logging.getLogger(__name__)
 
 
-def _run_git(args: list[str], cwd: str | Path, timeout: float = 5) -> subprocess.CompletedProcess:
+def _run_git(args: list[str], cwd: str | Path, timeout: float = 2) -> subprocess.CompletedProcess:
     return subprocess.run(
         ["git", *args],
         cwd=str(cwd),