fix(alembic): bridge ghost migration 2026_05_28_add_tool_definition_manifests

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 ...

scripts/fix_ghost_migration.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+# Fix ghost migration on production server
+# Run this INSIDE the api container or on the server
+
+echo "=== Checking for ghost migration file ==="
+find /app/alembic/versions -name "*tool_definition*" 2>/dev/null
+
+echo ""
+echo "=== Current alembic_version in DB ==="
+psql "$DATABASE_URL" -c "SELECT * FROM alembic_version;"
+
+echo ""
+echo "=== Checking if tool_types has definition_manifests column ==="
+psql "$DATABASE_URL" -c "\d tool_types" | grep -i manifest
+
+echo ""
+echo "=== Our known migration heads ==="
+grep -r "revision.*=" /app/alembic/versions/*.py | grep "2026_05_28"