Index Tab selected feedback, no-op guard, page-zero block, and auto-page creation

[No0ne558]

Description:

This PR implements three quality-of-life improvements to Index Tab buttons that together make it dramatically easier to build and navigate multi-page interfaces.

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What changed

Visual feedback — active tab highlights automatically

IndexTabZone::State() is overridden to return the selected state (1) whenever the terminal's current page matches the tab's jump_id. Because Zone::Draw() already uses the State() result to pick frame[state], texture[state], and color[state], the tab for the page you're on renders automatically in its configured selected appearance (edge, texture, font color). No new fields on Terminal are needed.

No-op guard — tapping your current tab does nothing

IndexTabZone::Touch() returns SIGNAL_IGNORED when the terminal is already on the tab's target page. This prevents a pointless re-jump and a screen flash when a user taps the tab for the page they're already viewing.

Block page number zero

ZoneDB::Add(Page*) — the single authoritative insertion point for all pages — now rejects any page with id == 0 with a ReportError. No page numbered zero can be created through any code path.

Auto-create a menu page when a new Index Tab button is saved

ZoneDB::NextAvailablePageID(int start_id, int page_size) is a new helper that walks up from start_id until it finds an unused page ID.

In Terminal::ReadZone(), when a brand-new ZONE_INDEX_TAB is saved with no jump target yet (JUMP_NONE), the system automatically:

1. Finds the first available page ID ≥ 60.
2. Creates a PAGE_ITEM menu page named after the button.
3. Registers it in the zone database.
4. Sets the button's jump to JUMP_NORMAL targeting the new page.

Editing an existing Index Tab that already has a configured jump is completely unaffected.

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Files changed

File	Change
button_zone.hh	Add State() and Touch() overrides to IndexTabZone
button_zone.cc	Implement both overrides
zone.hh	Declare ZoneDB::NextAvailablePageID()
zone.cc	Page-zero guard in ZoneDB::Add(); implement NextAvailablePageID()
terminal.cc	Auto-page-creation block in Terminal::ReadZone()
changelog.md	Entry under [Unreleased] → Added

6 files changed, 73 insertions(+), 1 deletion(-)

[GeneMosher]

Building and using any hospitality menu begins with the Index Page because it lists the Food and Beverage categories, or Families, which are the framework of the menu.

ViewTouch provides special buttons for the Index Page - Index Tabs, which are repeated on every Menu Item Page. The Index Page and Index Tab buttons make it possible for users to navigate to any Page in the Menu with a single touch, no matter where the user might be in the Menu.

There are also 'time of day' Index Pages and Index Tabs which allow Menu Pages to be either restricted to certain times of the day or, to put it another way, to be allowed to be available at certain times of the day.

The strength of ViewTouch is the versatility of tools available to ViewTouch Editors for building Menu interfaces that perfectly match the thoughts and words which guests use to express their menu selections. This is a unique requirement of point of sale software which I recognized even in 1979 when I first began developing my order entry program for my restaurant, Gene Mosher's Old Canal Cafe in Syracuse, New York, using the Apple II computer I had purchased in the Summer of 1977.

I must mention that Ariel has used AI to extend and modify the code to implement these newly integrated Editing features. Anyone is invited to follow his example to similarly improve the usability and value of the ViewTouch point of sale code base !