Add database migration for schema updates

When the registry server starts, it now automatically adds any missing
columns to existing tables. This prevents 500 errors when publishing
to a database created before newer columns were added.

Columns added by migration:
- scrutiny_status, scrutiny_report (tool scrutiny)
- source, source_url, source_json (tool attribution)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/cmdforge/registry/db.py

@@ -281,6 +281,39 @@ def connect_db(path: Path | None = None) -> sqlite3.Connection:
 def init_db(conn: sqlite3.Connection) -> None:
     conn.executescript(SCHEMA_SQL)
     conn.commit()
+    # Run migrations for existing databases
+    migrate_db(conn)
+
+
+def migrate_db(conn: sqlite3.Connection) -> None:
+    """Add missing columns to existing tables (for schema updates)."""
+    # Get existing columns in tools table
+    cursor = conn.execute("PRAGMA table_info(tools)")
+    existing_cols = {row[1] for row in cursor.fetchall()}
+
+    # Columns that may need to be added (column_name, type, default)
+    migrations = [
+        ("scrutiny_status", "TEXT", "'pending'"),
+        ("scrutiny_report", "TEXT", "NULL"),
+        ("source", "TEXT", "NULL"),
+        ("source_url", "TEXT", "NULL"),
+        ("source_json", "TEXT", "NULL"),
+    ]
+
+    for col_name, col_type, default in migrations:
+        if col_name not in existing_cols:
+            try:
+                conn.execute(f"ALTER TABLE tools ADD COLUMN {col_name} {col_type} DEFAULT {default}")
+                conn.commit()
+            except sqlite3.OperationalError:
+                pass  # Column might already exist or other issue
+
+    # Ensure indexes exist
+    try:
+        conn.execute("CREATE INDEX IF NOT EXISTS idx_tools_owner ON tools(owner)")
+        conn.commit()
+    except sqlite3.OperationalError:
+        pass
 
 
 def query_one(conn: sqlite3.Connection, sql: str, params: Iterable | None = None):