feat(documenteditor): add Pageless view toggle

[juliusknorr]

Pageless view for the document editor

Requires Euro-Office/sdkjs#53

Adds a Pageless toggle to the document editor's View tab. When enabled, the engine renders the document as one continuous sheet (no page gaps/outlines). Mirrors the existing Multiple Pages toggle end-to-end.

Changes

• view/ViewTab.js: new btnPageless toggle button, slot, click event, render, and textPageless string.
• controller/ViewTab.js: onPagelessMode handler + pages:pageless wiring; calls api.SetPagelessMode(...) and persists to localStorage["de-pageless-mode"].
• controller/Main.js: restores the saved preference on editor load so it survives reload.
• locale/en.json: DE.Views.ViewTab.textPageless (English; other locales fall back).

Notes

• Requires the engine API SetPagelessMode/GetPagelessMode (see the sdkjs PR).
• View preference only — per-user, does not modify the document or affect collaborators.
• Icon currently reuses the multiple-pages glyph as a placeholder; a dedicated icon can follow.

[chrip]

🔴 Critical: pages:pagelesschanged handler is dead code (controller/ViewTab.js:111-115)

The pages:pagelesschanged callback is never reached. Two things prevent it from firing:

1. No SDK callback: SetPagelessMode in the SDK (api.js of sdkjs PR #53) does not fire an asc_onPagelessMode callback. The engine does not emit a pageless change event back to web-apps.
2. No fireEvent call: onMultiplePages (controller/ViewTab.js:293) calls this.view.fireEvent('pages:multiplechanged', [pressed]). onPagelessMode (controller/ViewTab.js:298-303) does not fire any event.

As a result, the callback at lines 111-115 is unreachable. api.SetPagelessMode, localStorage.setBool, and btnPageless.toggle inside it never execute, leaving the button state and persistence broken after any programmatic state change.

Fix: Follow the onMultiplePages pattern. Remove api.SetPagelessMode() and localStorage.setBool() from onPagelessMode itself, and replace them with this.view.fireEvent('pages:pagelesschanged', [pressed]). The callback handler already contains those calls and will now actually execute. Additionally, Statusbar.js needs a corresponding listener on ViewTab.pages:pagelesschanged to sync the statusbar button, mirroring what exists for pages:multiplechanged.

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🟡 Missing zoomCustomMode() call (controller/ViewTab.js:298)

onMultiplePages calls this.api.zoomCustomMode() before SetMultipageViewMode. onPagelessMode omits this. If pageless mode should release fit-to-page/fit-to-width zoom constraints (which it almost certainly does as a continuous scroll view), this is a functional gap. Consider adding this.api.zoomCustomMode() before api.SetPagelessMode(pressed).

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🟡 No mutual exclusion with Multiple Pages

Multiple Pages and Pageless can be active simultaneously. The engine (HtmlPage.js in sdkjs PR #53) sets isPagelessMode independently of multipage mode. Having both enabled is likely an invalid or confusing visual state. Consider wiring them as a mutually exclusive group, or explicitly disable one when the other activates.

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🟡 Missing btnPageless.updateHint() in onAppReady (view/ViewTab.js:540-563)

All other buttons get their tooltips set in onAppReady (view/ViewTab.js:540-563), but btnPageless is skipped. Additionally, tipPageless is never defined in the text strings. Users will see no tooltip for the button.
Fix: Add tipPageless: 'Pageless mode' (or similar) to the text strings, and call this.btnPageless.updateHint(this.tipPageless) in onAppReady.

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🟢 Minor: Placeholder icon (view/ViewTab.js:320)

Reuses toolbar__icon btn-multiple-pages for the pageless button. Two adjacent identical icons are confusing. Needs a dedicated icon, or at least a tracked follow-up issue to resolve the placeholder.

Assisted-by: OpenCode:Qwen3.6-27B