Wireframe viewer: support deep-linking to a specific SVG (hash-write + route passthrough)

[TortoiseWolfe]

Summary

The wireframe viewer (.specify/extensions/wireframe/viewer/viewer.html) supports being opened on a specific SVG via #<feature>/<file>.svg — the boot sequence reads window.location.hash. But two gaps make deep-linking unusable in practice:

1. The hash is never written. Clicking a wireframe in the nav calls updateView() but doesn't update location.hash, so the address bar never reflects the current SVG — you can't copy a shareable link by browsing.
2. The Next.js /wireframes route ignores the URL. src/app/wireframes/page.tsx hardcodes getAssetUrl('/wireframes/viewer.html') and forwards no param, so tortoisewolfe.github.io/<repo>/wireframes/... can't deep-link into the iframe at all.

Proposed fix (implemented downstream in RescueDogs, offered upstream)

viewer.html — in updateView(), after updating the active nav state:

if (wf.path && window.location.hash.replace(/^#/, '') !== wf.path) {
  history.replaceState(null, '', '#' + wf.path);
}

Plus a hashchange listener so external hash changes (back/forward, a parent frame, a pasted link) select the matching wireframe. replaceState avoids piling a history entry on every click.

/wireframes route — make it an optional catch-all [[...slug]]:

• generateStaticParams enumerates public/wireframes/wireframes-manifest.json so /wireframes/<feature>/<file> prerenders under static export.
• Forward the slug to the iframe as a hash.
• Gotcha: drop the .svg extension from the URL slug — keeping it makes the route emit out/wireframes/<feature>/<file>.svg/index.html, which collides (EEXIST at export) with the real <file>.svg asset sync-wireframes.sh copies to the same path. Restore .svg when building the hash.

Why upstream

This lives in the vendored wireframe extension, so every fork (RescueDogs, HatCoatAndBoots, future template tracks) re-derives or loses the fix on an extension update. Landing it upstream makes deep-linkable wireframes a shared capability.

Reference

Downstream implementation: TortoiseWolfe/RescueDogs PR for feat/wireframe-deeplinks (viewer hash-write + [[...slug]] route + unit test; build/export verified with 63 deep-link pages, no collision).