feat(lib): migrate to SQLite WAL backend for robust concurrency (FW-L1)

- Replaces python fcntl.flock with SQLite BEGIN IMMEDIATE.
- Status/Reconcile read from SQLite SSOT, with YAML fallback.
- Explicitly documented tradeoff: YAML is no longer a real-time view.
- Handles PRAGMA wal_checkpoint(TRUNCATE) safely outside transactions.

skills/tmux-agent-orchestrate-monitor/scripts/reconcile.sh

@@ -237,8 +237,20 @@ now_iso = datetime.now(timezone.utc).strftime('%Y-%m-%dT%H:%M:%SZ')
 try:
     d
 except NameError:
-    with open(yaml_path) as f:
-        d = yaml.safe_load(f) or {}
+    import sqlite3
+    db_path = yaml_path.replace('.yaml', '.db')
+    d = {}
+    try:
+        if os.path.exists(db_path):
+            conn = sqlite3.connect(db_path, timeout=10.0)
+            row = conn.execute('SELECT data FROM state WHERE id=1').fetchone()
+            if row: d = json.loads(row[0])
+            conn.close()
+        elif os.path.exists(yaml_path):
+            with open(yaml_path) as f:
+                d = yaml.safe_load(f) or {}
+    except Exception:
+        pass
 
 drifts = []
 actions = []