feat: remove config/state mounts from built-in tool configs

- Remove pi_state and pi_config mounts from the pi-agent manifest.
- Add Alembic data migration to strip those mounts from existing DB rows.
- Remove opencode_home:/tmp volume and HOME=/tmp override from the opencode
  built-in compose template; config/state now belongs in config profiles.
- Workspace and SSH key mounts remain unchanged.

Quality gates: python3 -m py_compile, pytest (311 passed, 34 skipped),
npm run typecheck, npm run lint

apps/api/src/seeds/builtin_tool_types.py

@@ -103,11 +103,8 @@ services:
     image: node:20-slim
     container_name: {{TOOL_NAME}}
     working_dir: /workspace
-    environment:
-      - HOME=/tmp
     volumes:
       - {{REPO_PATH}}:/workspace
-      - opencode_home:/tmp
     ports:
       - "3000:3000"
     command: >
@@ -125,10 +122,7 @@ services:
              exec tail -f /dev/null"
     stdin_open: true
     tty: true
-    restart: unless-stopped
-
-volumes:
-  opencode_home:""",
+    restart: unless-stopped""",
                 "required_variables": ["REPO_PATH", "TOOL_NAME"],
             },
         ]