feat(spotlight): add Spotlight testing

[qeude]

Summary

Add Spotlight testing to Jean.

This introduces a Conductor-style Spotlight workflow where a worktree can be mirrored into the repository root for running and testing, while keeping the worktree as the source of truth.

Reference:
https://docs.conductor.build/guides/spotlight-testing

Included

• Spotlight enable/disable flow in the session modal
• keyboard support for Spotlight
• worktree-to-root Spotlight sync behavior
• restore of the original root state when Spotlight is disabled
• fallback to normal run behavior for base sessions
• targeted Spotlight tests

Validation

• bunx eslint src/components/chat/SessionChatModal.tsx src/hooks/useMainWindowEventListeners.ts src/services/spotlight.ts src/services/spotlight.test.ts
• bun run typecheck
• bun run test:run src/services/spotlight.test.ts

Notes

bun run check:all is currently failing in this workspace because of existing Rust clippy errors outside the scope of this change.