Drop outer Border wrapper in WorktreesOverviewModalView so Avalonia edge
resize handles reach the window frame. Add split pane to WorktreeModalView
with file tree on left and per-file unified diff on right; wire SelectedNode
via SelectedItem TwoWay binding + SelectionChanged fallback; add
GetFileDiffAsync to GitService.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Adds WorktreeModalView/ViewModel showing git status --porcelain as a
recursive file tree with M/A/D/? status badges. Wires the Worktree
button in AgentStripView to OpenWorktreeCommand on DetailsIslandViewModel.
Adds GetStatusPorcelainAsync to GitService.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
