Keep the demo's engine pin from going stale again, and name the version the arcade needs

[JSv4]

What was wrong

The Doom cartridge on the live demo halted with:

this engine renders a single block without its inline image, so the frame is in the .docx but never on screen

That message is the arcade's own capability probe, and it was telling the truth. The GitHub Pages demos load the library from jsDelivr at an exact version, and every page was still pinned to the release before 11.0.0. On that engine the Doom cartridge does everything except the part you can see: the WebAssembly engine boots, plays and logs (which is why the console in the bug report is full of healthy Doom output), replaceImage succeeds, and the 320×200 frame really is in the document — Save and reopen shows it. But the incremental single-block render that repaints the frame paragraph cloned the block's XML into a throwaway shell with neither a copy of the referenced media part nor an image handler, so WmlToHtmlConverter correctly omitted the w:drawing and the paragraph refreshed blank. The library fix shipped in 11.0.0; what was left was the pin.

The other console lines in the report are not ours and need no change: the try/try_table line is a Firefox deprecation warning about the .NET WebAssembly runtime's exception-handling opcodes, the Carlito line is Firefox's font-visibility setting refusing a locally installed font, and the source-map error is devtools failing to resolve a source map for a wasm: URL.

What this branch adds on top of main

main moved the pins in parallel (f8e347b), and this branch is merged with it — the arcade-row rewording from that commit is kept verbatim. What is left here is the part that stops the same thing happening at the next release:

The pin is now under test, because nothing was watching it. A stale pin is invisible to the browser specs: every arcade and social spec overrides ?engine= to the locally built bundle, which has always carried the fix, so the whole suite stayed green while the public site rendered nothing. docs/demo/tools/engine-pin.test.mjs reads the checked-in files with no browser and no network, and fails when:

• the pins disagree with each other (a half-moved pin is how you get a landing page on one engine and the arcade it frames on another);
• the pinned version falls below IMAGE_ENGINE_MINIMUM, a new export from ascii-arcade.js naming the oldest engine whose incremental render carries an inline image — so the arcade cannot ship pointed at an engine that renders Doom invisibly;
• RELEASE_ENGINE in npm/tests/social-demo.spec.ts drifts from the pages it guards.

A fourth check asks jsDelivr whether the pinned bundle is actually published — the failure mode of re-pinning ahead of a release — and is skipped unless DOCXODUS_CHECK_CDN=1, so the default run stays offline and deterministic. The suite is wired into npm run test:demo-logic, and therefore into every Playwright run's pretest.

Prose that recounts a past version is not a pin: the scan grandfathers the README's account of the observatory being pinned ahead of 9.6.0, and the rest of the historical wording avoids the docxodus@ prefix.

paintImage keeps its probe, and stops hardcoding the version. Anyone who points ?engine= at an older release still gets the halt rather than invisible frames; the message now reads the required version from IMAGE_ENGINE_MINIMUM and says to check the override.

Two more copies of the pin move with the rest: the copy-pasteable CDN examples in npm/src/embed.ts and npm/src/index.ts, which ship in the package's own doc comments — a reader who pastes one gets whatever engine it names. They are in the tested set now.

The Publish section of docs/demo/README.md records the full pin set and what the guard checks, and there is a CHANGELOG entry under [Unreleased].

Validation

• npm run test:demo-logic — 29 assertions across the five demo-logic suites, all passing, on the merge result.
• Both new failure paths were exercised rather than assumed: reverting one page's pin to the old version fails the agreement check naming that file, and raising IMAGE_ENGINE_MINIMUM above the pin fails the capability check with the explanation.
• DOCXODUS_CHECK_CDN=1 node --test docs/demo/tools/engine-pin.test.mjs passes against the live CDN (4/4), which is the real confirmation that 11.0.0 is servable.
• The Playwright suite could not run in this environment (it needs npm run build, which needs the wasm-tools workload); the only thing it sees from this branch is RELEASE_ENGINE, unchanged from main and now pinned to the pages by the offline test.

🤖 Generated with Claude Code

https://claude.ai/code/session_01PzrZihTdHGDcP3jLeBShBG