feat(pptx): add full-screen slideshow with keyboard controls

[Ege-BULUT]

Summary

• Adds a full-screen slideshow mode to the PPTX renderer, toggled with F5 or P.
• The existing scale box is moved into an overlay and inactive slide slots are hidden with CSS, so the engine's scoped slide styles keep applying and no slide nodes are cloned. A placeholder marks the original position so exiting restores the deck exactly.
• Controls mirror PowerPoint: ←/→ navigate, Home/End jump, Esc exits; click zones navigate, and a "Start slideshow" button with a keyboard hint sits above the deck.
• Three new i18n keys (presentation.slideshow.*) across zh/en/ja.

Verification

• pnpm type-check
• pnpm docs:build
• pnpm test:i18n
• pnpm verify:pptx-slideshow - self-hosts the built demo and runs 16 checks:
  • demo integration: deck renders, F5 opens, arrow/click/Home/End navigate, Esc restores, P re-enters
  • default (non-windowed) API: slideCount reports the deck, enterPresentation() opens, navigation and active-slide content work
  • active slide keeps its content after a viewport resize
  • two renderer instances: one P opens exactly one overlay
  • shadow-root native fullscreen exit closes the overlay
  • Enter/Space on the focused exit button exits instead of advancing
  • destroy/unmount while presenting removes the overlay
  • scroll position and scale transform restored exactly on exit
• pnpm verify:browser-smoke

Notes

• Related issue: none
• File types affected: pptx
• Deployment paths affected: none (renderer + demo only)
• presentationFullscreen: false lets hosts opt out of native fullscreen (the overlay stays position:fixed).

[wybaby168]

Thanks for the substantial work here. The happy path is promising, and I verified that the current 20-slide demo can enter, navigate, and exit when a server is started manually. I can't merge this head yet because the review found several reproducible correctness issues:

1. The new public @file-viewer/pptx API does not work with its default, documented configuration. slideCount only counts slideRecords, but the non-windowed path appends slides without creating those records, so enterPresentation() silently returns. With the bundled 20-slide sample I observed 20 rendered .slide nodes, slideCount === 0, and no overlay after enterPresentation().

2. Virtualization can remove the active slide during a presentation. After jumping to slide 20, a resize/window update can unmount that record because the windowing code still uses scroll-view geometry while the scale box is inside the fixed overlay. The active slot remains selected but has no child slide, producing a black presentation.

3. Each standard renderer instance installs its own document-level F5/P listener. With two PPTX viewers on one page, one P keypress opens two overlays. Please scope the shortcut to a focused/active viewer or use one global arbiter.

4. Native fullscreen ownership is detected incorrectly inside Shadow DOM. Chromium exposes the overlay through shadowRoot.fullscreenElement while document.fullscreenElement is the host, so ownsFullscreen stays false and a browser-native fullscreen exit leaves the fixed overlay open.

5. Exiting after entering from a scrolled deck loses the original scroll position because moving the scale box collapses the scroller and clamps scrollTop to zero. The placeholder restores DOM position, but not view position.

6. When the exit button has focus, Enter/Space is intercepted by the document presentation handler and advances the slide instead of activating the button.

The regression gate also needs hardening: pnpm verify:pptx-slideshow assumes an external server at 127.0.0.1:8081, is not run by Public CI, and only asserts slot markers, so an active but empty slot can pass. Please make it self-host the built demo and cover default/non-windowed API use, active-slide content after resize, two instances, Shadow DOM native fullscreen exit, focusable controls, unmount/failure cleanup, and exact scroll/transform restoration.

Locally passed on this exact head: full pnpm type-check, PPTX and presentation builds, pnpm docs:build, pnpm test:i18n, pnpm verify:browser-smoke, and the existing slideshow script after manually starting the built demo. These failures are runtime coverage gaps rather than compile failures.

[Ege-BULUT]

Addressed all six findings plus the regression-gate hardening. Each fix has a dedicated check in pnpm verify:pptx-slideshow (now self-hosted and wired into Public CI):

1. Non-windowed API - slideCount now counts every slide the worker sends (totalSlides), independent of the virtualization records, and enterPresentation() no longer bails on an empty record list. Non-windowed decks also get the active-slide toggle and hide rules (they append slides directly instead of in slots). Check 10.
2. Virtualization unmounting the active slide - the windowing code keeps the active slide and its neighbour mounted while presenting, so a resize cannot unmount the on-screen slide. Check 11.
3. One F5/P opens every viewer - a module-level arbiter makes the last-mounted/last-focused shell the only one that answers the shortcut. Check 12.
4. Shadow DOM fullscreen ownership - fullscreen is detected through the shadow root (shadowRoot.fullscreenElement) as well as the document, so a browser-native exit closes the overlay. Check 13.
5. Lost scroll position - the deck scroll is captured on enter and restored on exit after the scale box height is recomputed; the original transform is preserved. Check 16.
6. Enter/Space on the exit button - the presentation key handler skips interactive targets, so the focused control activates instead of advancing. Check 14.

The verify script now self-hosts the built demo (no external server), asserts active-slide content rather than slot markers, and covers unmount/failure cleanup (check 15) plus the two-instance and shadow-fullscreen paths. presentationFullscreen: false was added so hosts can opt out of native fullscreen.

[wybaby168]

Thanks — the original runtime blockers are fixed, and the browser gate passes. Two host-boundary blockers remain on the latest head:

• P/F5 opens the last-mounted viewer even when focus is on an unrelated host control, and prevents the host key event. Restrict shortcuts to an explicitly active/focused viewer and add an outside-focus regression.
• The document keydown listener is installed before PptxViewer.open() completes. If initialization rejects, no instance is returned, so the listener and shell remain. Clean up listeners, active state, and DOM on failure/abort, with a regression test.

Please also rebase onto current main before landing so the PPTX security fixes stay intact.

[wybaby168]

Maintainer fixes applied on the latest security baseline. Slideshow, sanitizer, build, type-check, unit, and browser smoke gates pass.

[wybaby168]

Merged after maintainer fixes and a clean main-branch CI run. Thanks for the contribution.