fix(backends,storage,core): setuid in exec wrapper, missing-column migration, runner config dir for mirror, tagged prompt sources

tests/test_db_migrate.py

@@ -0,0 +1,33 @@
+import sqlite3
+import tempfile
+from pathlib import Path
+
+from sqlmodel import select
+
+from beaver_gateway.storage import Database
+from beaver_gateway.storage.models import Conversation
+
+
+async def test_create_all_adds_missing_columns() -> None:
+    path = Path(tempfile.mkdtemp(prefix="beaver-migrate-")) / "old.db"
+    raw = sqlite3.connect(path)
+    raw.execute(
+        "CREATE TABLE conversations (id INTEGER PRIMARY KEY, frontend VARCHAR NOT NULL, "
+        "external_id VARCHAR NOT NULL, agent_name VARCHAR NOT NULL, "
+        "created_at DATETIME NOT NULL, updated_at DATETIME NOT NULL)"
+    )
+    raw.execute(
+        "INSERT INTO conversations VALUES (1, 'markdown', 'x', 'a', '2026-01-01', '2026-01-01')"
+    )
+    raw.commit()
+    raw.close()
+
+    db = Database(f"sqlite:///{path}")
+    await db.create_all()
+    async with db.session() as session:
+        conv = (await session.exec(select(Conversation))).one()
+        assert conv.session_id is None
+        conv.session_id = "sid"
+        session.add(conv)
+        await session.commit()
+    await db.dispose()