Hide Agent Node working-directory controls behind a popover

[Yuqing (mydmdm)]

Summary

• replace the always-visible working-directory override row with a Folder button beside the Agent selector
• show Profile, Profile directory, and effective directory context in a progressively disclosed popover
• mark explicit Node overrides on the trigger and provide an explicit restore-inheritance action
• retain read-only access after realization without changing persistence, validation, or locking semantics

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, 3038 tests)
• pnpm check:i18n

Follow-up hotfix for #273.