D8 canonical refresh: inline root-redirect HTML, drop template file

[Chris-Wolfgang]

Summary

Adopts the new canonical pattern (proven on D20-Dice b58861a, landed on repo-template/main via PR #408) for the gh-pages root landing page.

Changes (4 files)

• .github/workflows/docfx.yaml — synced from canonical. The root index.html is now built inline as a PowerShell string-array inside the Deploy docs to GitHub Pages step (no more Get-Content of a template file + regex -replace substitution). Only the page title is dynamic; the in-page version picker (public/version-picker.js) handles version switching from any docs page, so the root no longer needs a clickable list.

• .github/workflows/build-all-versions.yaml — same inline-HTML refactor on the parallel Generate root index.html step.

• .github/version-picker-template.html — DELETED. No workflow step references it anymore.

• docs/DOCFX-VERSION-PICKER.md — updated section 4, the gh-pages flow diagram, and the troubleshooting table to point at the new step names + log lines.

Why

The template-file indirection was pure overhead — the only dynamic piece was the page title (the repo name). Inlining the HTML in the workflow makes what gets produced visible at the call site and removes a file from every repo.

Bypass needed

Touches protected paths (.github/workflows/*.yaml, .github/version-picker-template.html), so the Detect .NET Projects guard will fail. Admin-bypass merge.

[Copilot]

Pull request overview

This PR updates the DocFX GitHub Pages deployment workflows to match a newer “canonical” pattern: generating the gh-pages root index.html inline (as a meta-refresh redirect to versions/latest/) and removing the standalone HTML template file previously used for the root landing page.

Changes:

• Inline generation of a redirect-only root index.html in both DocFX deploy workflows, removing reliance on .github/version-picker-template.html.
• Add a pre-build “overlay canonical docs assets from origin/main” option (docfx.yaml) plus additional deploy robustness (versions.json preservation guard, clearer git error handling, and safer root cleanup behavior).
• Delete .github/version-picker-template.html.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
.github/workflows/docfx.yaml	Adds optional canonical-asset overlay + versions.json preservation guard; switches gh-pages root index generation to inline redirect HTML.
.github/workflows/build-all-versions.yaml	Switches root index generation to inline redirect HTML; improves versions.json generation to omit tags that weren’t built; updates gh-pages action pin.
.github/version-picker-template.html	Removed (no longer referenced).