docs: publish versioned wiki automatically

[bifrost0x]

Summary

• publish the versioned docs/wiki source to the GitHub Wiki after trusted changes reach main
• route README readers to the live Wiki while keeping the reviewable source visible
• mirror all GitHub Markdown page variants and preserve non-page attachments

Safety

• runs only for main pushes or an explicit dispatch on main
• uses the repository token with scoped contents: write; no additional secret or PAT
• pins all external actions and serializes publication with a full pending queue
• rejects superseded revisions before work and immediately before the Wiki push
• refuses overlapping paths, linked/reparse metadata, external Gitdir pointers, and page symlinks before mutation

Validation

• python -m unittest tests.test_wiki_sync -v (8 passed)
• 43 documentation and supply-chain policy checks passed
• temporary live-Wiki clone: 27/27 pages matched, all supported stale Markdown variants removed, non-page attachment preserved
• git diff --check