feat(code): migrate header row items to Quill

[adamleithp]

Summary

• GitInteractionMenu: Replace Radix UI Button/DropdownMenu with Quill Button/ButtonGroup/DropdownMenu. Use variant="primary" for active split button. Hide dropdown when all actions disabled.
• ExternalAppsOpener: Replace raw <button> and Radix DropdownMenu with Quill ButtonGroup/Button/DropdownMenu. UX fix: call setLastUsedApp when selecting from dropdown so the main button icon updates to the user's last choice. Use onClick (not onSelect) for Base UI DropdownMenuItem. Wrap shortcuts in Kbd.
• DiffStatsBadge: Replace raw <button> with Quill Button (variant="outline", size="sm").
• HeaderRow: Remove left border separator, adjust padding for tighter layout.
• TaskDetail: Remove redundant Flex wrapper around ExternalAppsOpener.

Test plan

• Git interaction split button renders with primary (orange) styling
• Dropdown chevron hidden when all git actions disabled
• Git dropdown items open correct modals (commit, push, create PR, etc.)
• External apps: main button opens default app
• External apps: selecting from dropdown opens app AND updates main button icon
• External apps: ⌘O shortcut still works
• DiffStatsBadge toggles review panel
• Header row spacing looks correct, no left border

🤖 Generated with Claude Code

[greptile-apps]

Prompt To Fix All With AI

This is a comment left during a code review.
Path: apps/code/src/renderer/features/git-interaction/components/GitInteractionMenu.tsx
Line: 129-132

Comment:
**Use `onClick` instead of `onSelect`**

Same fix applied to `ExternalAppsOpener` — Quill's `DropdownMenuItem` is a Base UI component that uses `onClick`, not `onSelect`. The current `onSelect` prop is silently ignored, so clicking any item in the git dropdown does nothing.

```suggestion
              <DropdownMenuItem
                key={action.id}
                onClick={() => onSelect(action.id)}
              >
```

How can I resolve this? If you propose a fix, please make it concise.

_{Reviews (1): Last reviewed commit: "fix(code): polish header row items and f..." | Re-trigger Greptile}

[charlesvien]

LGTM!

[charlesvien]

• feat(code): migrate header row items to Quill #1850 👈 (View in Graphite)
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[charlesvien]

LGTM