Paginated commit history for the current ref, commit detail with
distinguished added/modified/deleted/renamed file status, bounded and
explicitly-truncated patch text, and a ref comparison flow validating
one entered ref against the currently open ref as base.
Reuses TASK-004's listCommits and this session's own TASK-009
HistoryRepository; no shared/domain file touched. Entry point is a new
history button on the existing code browser header.
Self-review caught and fixed a bug before writing tests: a failed
commit-detail fetch discarded which commit had failed, so retry
silently reloaded the whole list instead of re-fetching the commit the
user tried to open.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
