Publish searchable, revision-aware documentation

[ostomachion]

Change

Build a searchable DocFX site from the existing Markdown, with concise navigation and links to each page's source. Documentation links remain relative under any site base path; links to repository files resolve to the exact build commit, so previews and older releases do not drift to main. Generated output stays untracked and the temporary foundation plan is excluded.

Both selected Ubuntu PR lanes validate the rendered site through the required build-test gate. A separate manual workflow rebuilds protected main and publishes its checked artifact through the main-only, reviewer-protected github-pages environment. Pages is configured for GitHub Actions with HTTPS. Actual deployment and hosted browser acceptance follow this merge and will be recorded separately.

Validation

• pwsh ./scripts/check.ps1 full -Serial: required solution, content/policy, frontend packaging, and isolated shell gates.
• pwsh ./scripts/check-docs.ps1: 27 pages, rendered local links and anchors, search/source-link inventory, and four deliberate-defect regression groups, including two source revisions and relative page links.
• Independent review of revision-aware link resolution; final diff inspection.

Section 17's engine example/API reference remains open until the first engine slice exists. Existing uncommitted section 16 browser-testing work is excluded.

AI assistance was used for implementation, tests, documentation, and independent code inspection. Local automated checks are distinct from the forthcoming hosted deployment and browser checks.