fix(web-ui): improve session archive feedback and cleanup

[kev1n77]

Summary

• Show a success notification after archiving a single session.
• Tell users where to find archived sessions: Settings → Archived Sessions, for both single and bulk actions.
• Clear pending session-open intents and transitions during archiving, matching deletion behavior.
• Update English, Simplified Chinese, and Traditional Chinese notification text.

Type and Areas

Type: Bug fix / UI/UX

Areas: Web UI, session management, internationalization

Motivation / Impact

Provide clear feedback after archiving and help users locate archived sessions. Prevent stale session-open state from affecting the UI while preserving immediate, confirmation-free archiving.

Verification

• pnpm --dir src/web-ui run test:run src/app/services/sessionSceneLifecycle.test.ts src/flow_chat/services/sessionActivation.test.ts src/flow_chat/services/storeSync.test.ts src/app/stores/sceneStore.test.ts src/flow_chat/services/flow-chat-manager/SessionModule.test.ts src/app/components/NavPanel/sections/sessions/sessionActionConfirmation.test.ts
  • Passed: 6 test files, 88 tests.
• pnpm run check:web: passed.
• pnpm run i18n:audit: passed with 0 warnings.
• git diff --check: passed.

Reviewer Notes

• Changes are limited to frontend feedback and state cleanup. No backend protocol or persisted format changes.
• Remote workspace, remote control, Peer Device Mode, and Detached Dispatch scenarios were not verified on live devices.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable.