Keyboard navigation for sidebar file list (Tab to focus, arrows to move, Enter/Space to jump)

[IgorCandido]

Summary

Add true keyboard-driven sidebar file navigation, analogous to clicking a file in the sidebar with the mouse.

Currently, from reading src/ui/components/chrome/HelpDialog.tsx and the useAppKeyboardShortcuts wiring, the sidebar has:

• Tab — toggle files ↔ filter focus state
• / — focus the filter input
• [ / ] — prev/next hunk (crosses file boundaries)
• Mouse click on a file — jumps diff panel to that file's header

But there's no way, with focus in the "files" area, to move up/down the file list with the keyboard and activate a file. Tab toggles the focus flag but there are no arrow/j/k handlers bound while focusArea === "files", and no Enter/Space activation for the highlighted file. So practically the sidebar is mouse-only for file selection.

Requested behavior

1. Tab (or dedicated key) puts focus in the sidebar file list, with a visible focused-row indicator.
2. ↑ / ↓ (and ideally j / k) move the focused row in the sidebar without yet changing the diff pane.
3. Enter or Space on the focused row activates that file — same effect as a mouse click: align the diff viewport to the top of that file's header (equivalent to jumpToFile(fileId, 0, { alignFileHeaderTop: true })).
4. Tab again (or Esc) returns focus to the diff pane so all the existing diff-nav keys (], [, j, k, Space, etc.) resume working.

This would cleanly mirror the mouse flow — hover/click → jump — without needing the mouse, and is the natural companion to the filter (/) + Enter flow you already have.

Why it matters

Reviewers using tmux / terminal multiplexers / remote sessions / tiling WMs frequently can't or don't want to use the mouse. Multi-file reviews currently require either / + type-filename repeatedly, or walking every hunk with ] through files you don't care about. A sidebar that responds to keyboard focus + activation would make Hunk fully keyboard-first and significantly faster for large changesets.

Notes

• Filed via Claude Code on behalf of a user dictating intent — feature request, not a bug report.
• Verified against hunkdiff@0.10.0 installed via npm and against main source in this repo.
• Thanks for building Hunk — it's already an excellent tool; hope this helps prioritize.