feat(browser): adopt Ghostty v1.4 WASM through a maintained upstream wrapper

Problem

@openclaw/libterminal currently pins ghostty-web@0.4.0, whose bundled WASM predates Ghostty's v1.4.0 VT throughput work and native libghostty-vt terminal/render APIs.

Ghostty's July 2026 parser changes report roughly 1.5x to 6x throughput improvements, but those changes are currently available only on Ghostty main/tip. Adopting an unreleased commit or maintaining a private ABI patch in this repository would make libterminal responsible for an unstable upstream boundary.

Upstream gates

Do not start the dependency upgrade until both conditions are true:

• Ghostty publishes a stable v1.4.0 tag.
• A maintained upstream package publishes a Ghostty v1.4-compatible browser/WASM wrapper that provides the runtime and terminal surface libterminal consumes.

Tracking:

• Ghostty v1.4.0 milestone: https://github.com/ghostty-org/ghostty/milestone/12
• Ghostty VT throughput work: https://github.com/ghostty-org/ghostty/pull/13220
• Ghostty releases/tags: https://github.com/ghostty-org/ghostty/tags
• Current ghostty-web Ghostty upgrade work: https://github.com/coder/ghostty-web/pull/169
• Current ghostty-web release candidate: https://github.com/coder/ghostty-web/pull/182

Ownership boundary

libterminal must not fork, patch, or port the Ghostty C/WASM ABI.

Consume a maintained upstream release with a reproducible build and stable package contract. If no compatible upstream wrapper is published, leave this issue blocked rather than importing that ABI maintenance burden into libterminal.

Proposed work

• Replace the ghostty-web@0.4.0 pin with the stable compatible release.
• Confirm the wrapper still exposes the browser runtime surface used by loadGhosttyRuntime, including initialization, terminal construction, fitting, writes, resize, disposal, and input events.
• Regenerate the embedded Worker module, WASM, and browser-external assets with pnpm run generate:worker-assets.
• Verify Node asset serving still resolves the exact module and WASM shipped by the pinned package.
• Re-evaluate the default-color query compatibility responder. Remove or narrow it only if the new wrapper demonstrably emits the required OSC 10-12 responses itself.
• Add an Unreleased changelog entry describing the runtime dependency and performance change.

Performance evidence

Capture comparable before/after results using the existing ghostty-web@0.4.0 build as the baseline:

• sustained terminal write/parse throughput for plain text, Unicode/CJK, and escape-heavy output
• end-to-end browser write-to-render time under high output
• startup/WASM initialization time
• shipped WASM and generated Worker asset size
• peak memory under a bounded scrollback workload

The goal is to prove a meaningful product-level improvement, not repeat upstream parser-only benchmark claims.

Acceptance criteria

• The dependency is pinned to a stable published version, not Ghostty main, tip, a Git commit, or a locally patched artifact.
• No Ghostty ABI implementation or compatibility fork is added to this repository.
• Existing browser, Worker, and Node asset APIs remain compatible.
• Focused runtime tests and asset byte-integrity tests pass.
• Browser smoke proves a nonblank terminal, input, resize, disposal, and sustained high-output rendering.
• Before/after performance and artifact-size results are recorded in the pull request.
• pnpm test, pnpm test:browser, pnpm check, and pnpm run check:release pass.

First verify that Ghostty v1.4.0 and a maintained compatible browser/WASM wrapper are published; otherwise leave the issue blocked. Inspect the loadGhosttyRuntime surface and run pnpm run generate:worker-assets, then review the focused runtime and asset-integrity tests. Done means the stable dependency, browser/Worker/Node assets, smoke tests, performance results, and required pnpm checks all pass.