fix(project-tools): prevent Git review action menu drift

[su-fen]

Summary

• decouple Git review section-menu positioning from its scale animation
• anchor staged and working-change action menus to the trigger right edge with stable boundary correction
• add GUI and WebUI regression coverage that prevents transform-based positioning from returning

Root cause

The menu used translateX for right alignment on the same element whose entry animation also controlled transform. During the animation, layout measurement observed the temporary scale-only transform and applied an incorrect clamp correction; when the animation ended, translateX returned and shifted the menu again.

Validation

• node --test crates/agent-gui/test/settings/git-review-menu-position.test.mjs
• node scripts/check-mirror.mjs
• GUI: npm run build -- --logLevel error
• WebUI: npm run build -- --logLevel error
• git diff --check