fix(tabs): restore standard tab interactions - #86

Summary

• make the whole visible tab body selectable while keeping the close control independent
• support Control-Tab and Control-Shift-Tab cycling with guarded empty/single-tab behavior
• support middle-click close without changing the selected tab first
• preserve rename, context-menu, and accessibility behavior

Verification

• RED: GitHub Actions run 33452178623
• GREEN: GitHub Actions run 33454077403
  • 8 focused TabNavigationTests
  • full suite: 110 passed, 17 skipped
  • swift build
• final whole-branch review: no Critical, Important, or Minor findings

Manual pre-merge check

Please exercise the recorded macOS pointer/keyboard/rename/context-menu/accessibility matrix. Public NSHostingView inspection cannot reliably prove SwiftUI's internal event-routing regions, so this remains an explicit live-app gate.

Closes #62