feat: add commands to open worktree paths

[nelson870708]

Pull Request

1. Summary

Add worktree context menu actions to open a worktree in a new VS Code window or reveal it in the file explorer. Also make worktree tree items open the worktree directly when selected.

2. Related Issue

• Closes [FEATURE] Improve Worktree UX: Add "Open" and "Reveal" actions for easier navigation #35

3. Changes

Extension (src/)

• extension.ts
• views/worktrees-view.ts

Other (build, config, docs, etc.)

• package.json

4. Type of Change

• New feature
• Bug fix
• Refactoring (no functional changes)
• Style / UI update
• i18n (localization) addition or update
• Build / configuration change
• Documentation update
• Test addition or update

5. Testing

• npm test passed
• npm run lint passed
• Manually tested via VS Code Extension Host
• Verified in both dark and light themes (if UI was changed)

6. Screenshots (optional)

NA

7. Checklist

• New message types are defined in message-bus.ts (if applicable)
• UI strings are added to both en.ts and ko.ts (if applicable)
• Extension-side strings are added to both l10n/bundle.l10n.json and bundle.l10n.ko.json (if applicable)
• No leftover console.log or debug code

[the0807]

Thanks for the contribution, @nelson870708! This has been merged.