Add back and forward navigation history

[jongio]

Problem

grut encourages jumping between files, commits, PRs, issues, branches, and previews. After following several reactive selections, it is easy to lose the previous context and hard to get back to the file or GitHub item that started the investigation.

Proposed solution

Track a small navigation history of selection contexts in the TUI layer, covering file tree paths, commits, GitHub items, and preview targets. Add back and forward keybindings such as Alt+Left and Alt+Right. Restoring a history entry should refocus the relevant panel and re-emit the existing selection message so dependent panels update through the current reactive panel system.

User impact

Developers can explore a change, inspect related commits or PRs, then return to the starting point without rebuilding the same panel state by hand.

Acceptance criteria

• File, commit, branch, issue, PR, and workflow selections are recorded as navigation entries.
• Back and forward keybindings restore prior selections and update dependent panels through existing messages.
• Consecutive duplicate selections are collapsed and history is reset safely when the repo root changes.

Notes

Complexity: M • Priority: 3