resilient memory sync: decouple push/pull, startup full resync, auth failure handling

- Decouple push and pull in _sync_once() so pull always runs even if push fails
- Add startup full resync to catch drift from other agents and schema changes
- Add periodic full resync every ~10 minutes for continuous drift correction
- Add auth failure detection (401/403) with graceful SQLite-only degradation
- Add /api/auth-check endpoint for lightweight key validation
- Add retry cap (5 attempts) on pending ops to prevent infinite queue buildup
- Add orphan reconciliation: push local-only records with content dedup
- Add memory_count MCP tool for sync diagnostics
- Add version-based SQLite schema migration (PRAGMA user_version)
- Fix API key in ~/.claude.json to match server
- Update README with sync resilience docs, test structure, project layout
- Add 30 new tests covering all new behaviors (155 total, all passing)

tests/test_api.py

@@ -99,6 +99,20 @@ async def test_health_endpoint_no_auth(client):
         assert resp.json() == {"status": "ok"}
 
 
+@pytest.mark.asyncio
+async def test_auth_check_endpoint(client):
+    ac, conn, app_mod = client
+    async with ac:
+        resp = await ac.get(
+            "/api/auth-check",
+            headers={"Authorization": "Bearer test-key"},
+        )
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["status"] == "ok"
+    assert data["user_id"] == "testuser"
+
+
 @pytest.mark.asyncio
 async def test_store_memory_creates_record_with_user_id(client):
     ac, conn, app_mod = client