fix: Mouse Back/Forward support in webviews + few bugfixes (#3141)

- Add Mouse-3/Mouse-4 (back/forward) navigation support in webviews
- Add COLORTERM=truecolor env variable for terminal sessions
- Fix AI button width calculation when button is hidden
- Fix setSizeAndPosition animation on tab layout updates
- Increase DevInitTimeout for slower startup scenarios
- Update .gitignore and package-lock.json

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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>