feat(tui): navigate panels via Up/Down arrow overflow at list boundaries

[varshaprasad96]

Summary

When the cursor reaches the boundary of a TUI dashboard panel list, Up/Down arrow keys now overflow into the adjacent panel instead of clamping silently. Down at the bottom of a panel moves focus to the next panel (cursor at first item); Up at the top moves to the previous panel (cursor at last item). Empty panels are skipped. The ring wraps: Gateways → Providers/GlobalSettings → Sandboxes → Gateways.

Related Issue

Closes #2273

Changes

• Added DASHBOARD_PANELS const array defining the panel ring order
• Added panel_item_count() helper that returns item count for any panel, respecting the active middle-pane tab (Providers vs GlobalSettings)
• Added set_panel_cursor() helper to set the selected index for any panel
• Added overflow_focus_down() and overflow_focus_up() methods that walk the panel ring to find the next/previous non-empty panel
• Modified all four dashboard key handlers (handle_gateways_key, handle_providers_key, handle_global_settings_key, handle_sandboxes_key) to call overflow helpers at list boundaries instead of clamping

Testing

• rustfmt --edition 2024 --check passes
• cargo check -p openshell-tui compiles cleanly
• Unit tests added/updated — App::new requires a gRPC client, making isolated unit tests impractical without test infrastructure changes
• E2E tests added/updated (if applicable)
• Manually tested with a live gateway and sandbox:
  • Down at bottom of each panel → moves to next panel (cursor at first item)
  • Up at top of each panel → moves to previous panel (cursor at last item)
  • Wrap-around works in both directions
  • Empty panels are skipped
  • Mid-list Up/Down scrolls normally within a panel
  • TAB navigation unaffected
  • Middle pane tab switching (h/l) unaffected
  • GlobalSettings tab respects overflow correctly

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)

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[github-actions]

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[varshaprasad96]

I have read the DCO document and I hereby sign the DCO.

[johntmyers]

recheck

[johntmyers]

gator-agent

PR Review Status

Validation: This is a small, concentrated TUI enhancement implementing the clear user path in #2273. The change stays within the dashboard navigation subsystem and covers the Providers/Global Settings middle-pane variant.

Head SHA: b3251b8bbefc65b99fd8cef1f7f8c1ba63c9498b

Thanks @johntmyers — I checked the current head after your recheck comment, including the full diff, surrounding list-refresh behavior, linked issue requirements, docs impact, and existing checks.

Review findings:

• Author action required: The four Up handlers check only whether the selected cursor is greater than zero. When a previously populated gateways, providers, global-settings, or sandboxes list becomes empty, refresh logic can leave a nonzero cursor behind. Pressing Up then decrements that invisible cursor instead of immediately skipping the empty panel. Please gate each decrement on the active list still having items, as the Down handlers already do (for example, self.provider_count > 0 && self.provider_selected > 0), with equivalent guards for the other three lists.
• Automated coverage is recommended for forward/backward wraparound, consecutive empty panels, both middle-pane tabs, and a list becoming empty with a stale cursor. The ring calculation can be extracted into a pure helper without constructing a gRPC-backed App.

Docs: Missing for this direct user-facing keyboard behavior. Please add a short dashboard-navigation note to docs/sandboxes/manage-sandboxes.mdx describing Tab/Shift+Tab and Up/Down or j/k boundary overflow. No docs/index.yml change is needed because the existing page is already in navigation.

E2E: No test:* label is needed for this local TUI focus-state change.

Next state: gator:in-review

[johntmyers]

/ok to test b3251b8