fix lanes tab

[arul28]

Summary by CodeRabbit

• New Features

  • Updated work pane with dedicated entry buttons, per‑lane session management, background refreshes, and an empty state when no lane is selected.
  • Centralized dialog shell for consistent headers, icons, busy/close behavior, and cleaner dialog layouts.
  • PR UX: richer PR toasts, CI "running" indicator, and a merge-bypass option.

• Behavior

  • Improved rebase target resolution and post-create/attach navigation focusing.

• Tests

  • Added/expanded tests for rebases, PR polling, and PR detail behaviors.

• Style

  • Restyled New Lane dropdown, dialog layouts, labels, and error presentation.