Fix browser runtime wakes, fonts, touch and text input

[Gratenes]

Summary

Companion browser runtime changes for zeronsh/zeron#319.

• Keep dispatcher work running when Atomics.waitAsync returns synchronously; parse asynchronous results without confusing values and promises.
• Include the eight required IBM Plex Sans/Lilex font assets and upstream OFL licenses (sourced from Zed revision f14fea9).
• Coalesce resize renders and handle mobile viewport/keyboard layout.
• Preserve pointer ownership when another pointer is cancelled or loses capture; allow small finger movement without cancelling taps.
• Handle mobile beforeinput deletion using grapheme-safe UTF-16 ranges and prevent browser defaults for handled keydowns.
• Add a focused hosted runtime test gate.

Validation

Locally executed with nightly-2026-09-08:

• 5 Node/WASM regressions passed: synchronous/asynchronous wait-result parsing, pointer ownership, touch slop, and handled-keydown defaults. These execute with wasm-bindgen-test, rather than only compiling.
• 4 native Unicode regressions passed: emoji, combining marks, ZWJ sequences, selection preservation and invalid caret boundaries.
• Production WASM compilation and focused Clippy checks passed.
• The downstream shared web application release build passes with the published runtime implementation pinned to c1700b8de27a07b5bc1a190440b64e7323c008f9; the later runtime commit only corrects CI setup.

Commands: crates/gpui_web/tests/README.md.
Hosted checks: Web runtime workflow.

Remaining / landing order

• The author has manually verified phone taps, scrolling, keyboard behavior and popovers. Device/browser versions and the tested revision were not recorded.
• Phone copy/paste and emoji checks remain with the author; keep this draft until that check is recorded.
• These are focused policy/helper regressions, not a full DOM event integration suite or full zui workspace test run.
• Merge this runtime PR first, then move the companion web dependency to the resulting published zeronsh/zui revision and rerun its locked build.

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[Gratenes]

Updated to d282d50 and marked ready for review.

Includes the bundled color emoji, touch-focus tracking and browser keyboard/input fixes. Added CI coverage for Unicode deletion, touch-focus policy, emoji rendering and browser DOM focus.

Local checks passed, including the real headless Firefox DOM test with the lock-matched wasm-bindgen runner. I’ve also verified the integrated behavior in the staging app.

This should land before zeron #319, which will then be repinned to the resulting upstream revision.

[Gratenes]

Good morning — I did an additional review sweep of the browser runtime changes before asking for another review.

The sweep found one pointer-cancellation issue: browsers commonly report PointerEvent.button == -1 for pointercancel and lostpointercapture. This caused cancelled right- and middle-button gestures to emit a left-button release.

Both terminal paths now use the button recorded during pointer-down. This preserves the original button and prevents duplicate releases if cancellation and capture loss both fire.

I also reviewed the broader runtime changes again, with particular attention to:

1. Touch scrolling, pointer capture and cancelled gestures.

2. Synchronous touch-to-editor focus for mobile keyboards.

3. Browser text input, Unicode deletion and IME behavior.

4. Resize scheduling and forced rendering after viewport changes.

5. Cross-thread dispatcher wake handling.

6. Bundled text and color-emoji font fallback.

7. Cached-paint input registration and the cross-platform PlatformWindow addition.

No additional merge-blocking issues were found. The remaining suggestions were optional browser-test hardening for complete pointer sequences and cross-browser IME event ordering.

This PR should still land before zeron #319 so that the application PR can be repinned to the actual upstream zui merge SHA.