The production database was stamped with a migration that no longer exists
in the codebase (created on another branch, applied, then removed). This
adds a no-op bridge migration so Alembic can reconcile the DB state.
- Create bridge migration 2026_05_28_add_tool_definition_manifests (no-op)
- Re-chain terminal_sessions migration to depend on the bridge
- Fixes startup failure: Can't locate revision identified by ...
