skip header items when enabling the InkHUD menu cursor

[zeropt]

Modify onButtonShortPress() and onNavDown() so that when revealing the cursor by setting cursorShown to true, they select the first non-header item. onNavUp() functions similarly but selects the last non-header item.

• I have tested that my proposed changes behave as described.
• I have tested that my proposed changes do not cause any obvious regressions on the following devices:
  • Seeed Wio Tracker L1 E-ink

[Copilot]

Pull request overview

Updates InkHUD’s menu navigation so that when the menu cursor is first revealed, it skips over non-selectable header items and lands on the first/last actionable entry. This improves usability on menus that include section headers.

Changes:

• Update onButtonShortPress() to select the first non-header item when showing the cursor.
• Update onNavDown() similarly to select the first non-header item when showing the cursor.
• Update onNavUp() to select the last non-header item when showing the cursor.

[Copilot]

onNavUp() sets cursor = items.size() - 1 without guarding for items.empty(). If the items list is empty (e.g., a transient state during page changes), this underflows and items.at(cursor) will throw/abort. Add an early items.empty() check (and keep cursorShown false) before computing the last index, similar to the defensive handling used in onNavDown()/onButtonShortPress().

[zeropt]

This doesn't seem to be checked in any of the other places where the cursor moved or set. Should I add this guard everywhere the cursor is moved?

[Copilot]

The “select first non-header item” logic is duplicated in both onButtonShortPress() and onNavDown(). Consider extracting it into a small helper (and similarly for the “select last non-header” logic) to keep cursor-reveal behavior consistent and reduce the chance of future drift when header-handling changes.