Inspector trailing-slash Pages 404

Traceability

• Spec ID: inspector-trailing-slash
• Story: #132
• Status: Implemented

Intent

GitHub Pages currently 404s https://qoderai.github.io/better-harness/inspector/ while the slash-less URL is 200. The homepage, README, and some navbar links still point at the trailing-slash URL. No-JS readers, crawlers, and link checkers should get the Inspector page instead of a 404 HTML document.

Keep trailingSlash: false as the canonical URL policy. Do not flip the whole site to directory URLs.

Acceptance Scenarios

• AC-1: After a production docs build, GitHub Pages-style static lookup finds both inspector.html and inspector/index.html for English and Simplified Chinese. Serving either path returns Inspector HTML, not 404.html.
• AC-2: Homepage Inspector preview and "Open the interactive sample" links use the slash-less /inspector path. Navbar Inspector uses the same slash-less path.
• AC-3: README English and Simplified Chinese Inspector sample URLs use https://qoderai.github.io/better-harness/inspector without a trailing slash.
• AC-4: Canonical, sitemap, and Open Graph URLs remain slash-less /better-harness/inspector. The trailing-slash file is an alias for static hosts, not a second canonical route.
• AC-5: Existing demo directory routes such as /demo/harness-inspector/ keep their trailing slash because they are real index.html directories, not Docusaurus page aliases.

Non-goals

• Changing trailingSlash for the whole Docusaurus site.
• Adding a GitHub Pages 301/302, which static Pages cannot emit for this host.
• Rewriting every historical /inspector/ mention in older specs.
• Changing Inspector demo iframe content, Workbench behavior, or locales.

Plan and Tasks

1. Keep docs/docusaurus.config.js trailingSlash: false.
2. Add a postbuild copy of inspector.html to inspector/index.html for en and zh-Hans, so Pages serves /inspector/ as 200.
3. Point homepage and navbar Inspector links at /inspector.
4. Point README Inspector sample URLs at the slash-less public URL.
5. Add focused tests that assert the alias files, postbuild wiring, and README public URLs without grepping the whole repository.

Decision rationale: GitHub Pages serves file.html for /file and file/index.html for /file/, but does not redirect between them. Docusaurus trailingSlash: false only emits inspector.html, which is why the homepage trailing-slash href 404s. Copying the same HTML into inspector/index.html makes both URLs 200 without changing canonical URLs. Pages still cannot 301.

Test and Review Evidence

• AC-1: focused Vitest coverage copies a fake inspector.html into a temp build tree and asserts English and zh-Hans inspector/index.html exist with the same Inspector title, not 404 HTML.
• AC-1: docs/package.json postbuild runs the alias step after docusaurus build.
• AC-2/AC-3: focused assertions on homepage useBaseUrl("/inspector"), navbar to: "/inspector", and README public URLs.
• AC-4/AC-5: production docs build leaves sitemap/canonical slash-less and keeps /demo/harness-inspector/ as a directory route.
• Manual: curl -sSI both public URLs after Pages deploy; neither is 404.