feat: 🗂 TUI — Navigation & result management (EPIC)

[shouze]

Overview

This epic tracks the implementation of the Navigation & result management features for the TUI, as described in the Roadmap #63.

Features in scope

Priority	Feature	Sub-issue
🔴 high	Global fold / unfold — single shortcut to collapse or expand all repos at once	#TBD
🟡 medium	Fast navigation — gg/G (top/bottom) and Page Up / Page Down	#TBD
🟢 nice-to-have	Open in browser — o shortcut to open the GitHub URL of the focused result	#TBD

Out of scope: 🟡 Team section selection (a/n on a team section header) — tracked separately.

Branch strategy

• Epic branch: feat/tui-navigation-result-management
• Each sub-issue is developed on its own branch and merged into the epic branch via PR.
• The epic branch is merged into main once all sub-issues are done.

Acceptance criteria

• Global fold/unfold shortcut works (e.g. z or similar) and toggles all repo sections
• gg jumps to top, G jumps to bottom, Page Up / Page Down scroll by a full page
• o opens the focused result's GitHub URL in the default browser (open on macOS, xdg-open on Linux)
• All existing tests remain green (bun test)
• bun run lint, bun run format:check, bun run knip all pass
• Keyboard shortcuts documented in docs/reference/keyboard-shortcuts.md