feat: add git-consistent memory gateway architecture

gateway/app/locks.py

@@ -0,0 +1,37 @@
+from __future__ import annotations
+
+from contextlib import contextmanager
+from dataclasses import dataclass
+import threading
+import time
+
+
+@dataclass
+class LockStats:
+    key: str
+    wait_ms: int
+
+
+class WorkspaceLockManager:
+    def __init__(self) -> None:
+        self._locks: dict[str, threading.Lock] = {}
+        self._guard = threading.Lock()
+
+    def _get_lock(self, key: str) -> threading.Lock:
+        with self._guard:
+            lock = self._locks.get(key)
+            if lock is None:
+                lock = threading.Lock()
+                self._locks[key] = lock
+            return lock
+
+    @contextmanager
+    def acquire(self, key: str):
+        lock = self._get_lock(key)
+        started = time.perf_counter()
+        lock.acquire()
+        wait_ms = int((time.perf_counter() - started) * 1000)
+        try:
+            yield LockStats(key=key, wait_ms=wait_ms)
+        finally:
+            lock.release()