feat: skip delete confirmation dialog when Option key is held

[matt2e]

Summary

• When the Option (Alt) key is held while clicking a delete button on timeline items (commits, notes, reviews, images), the confirmation dialog is bypassed and the item is deleted immediately
• Propagates the altKey state from the mouse event through the component hierarchy (TimelineRow → BranchTimeline → BranchCard)
• Refactors delete handlers to extract the deletion logic into a doDelete closure, used by both the instant-delete path and the confirmation dialog's onConfirm callback

Test plan

• Click delete on a timeline item without holding Option — confirm dialog should appear as before
• Hold Option and click delete on a commit, note, review, and image — each should delete immediately without confirmation
• Verify error handling still works (e.g., failed deletes show error notification)

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