Add persistent local agent tools

migrations/20260725140000_add_tool_messages/down.sql

@@ -0,0 +1 @@
+ALTER TABLE messages DROP COLUMN tool;

migrations/20260725140000_add_tool_messages/up.sql

@@ -0,0 +1,2 @@
+ALTER TABLE messages ADD COLUMN tool BOOLEAN NOT NULL DEFAULT FALSE
+    CHECK (tool IN (FALSE, TRUE));