Allow Agent Nodes to override Profile working directories

[Yuqing (mydmdm)]

Summary

• expose the existing agentLaunchOverrides.workingDirPath contract in editable external Agent Nodes
• keep empty values as Profile inheritance and preserve explicit overrides across Profile changes
• retain server/Agentlet validation and realization locking, with inline failure feedback and a locked read-only summary
• document the ownership model and add focused persistence/UI coverage

Validation

• pnpm typecheck
• pnpm format
• pnpm lint:fix
• pnpm --filter @huabu/web test -- src/components/Panels/ChatPanel/WorkingDirectoryOverride.test.tsx src/store/conversationOwner.test.ts (274 files, 3036 tests)
• pnpm check:i18n

Closes #269