docs: clickable Key links, footer source link, move operator material to co-op/ops-docs

- README: render the Key links as real Markdown links (mailto: for the
  contact address); drop the 'lives in a public git repository' note now
  that the footer carries the source link.
- mkdocs.yml: add a theme override (custom_dir: overrides) that puts a
  'Documentation source' link in the footer of every page.
- Move the operator runbook, maintenance notes and incident write-up out
  of the published site into the git-only co-op/ops-docs repository;
  remove them from the nav and repoint cross-references at Gitea.

README.md

@@ -20,13 +20,13 @@ funded through our [Open Collective](https://opencollective.com/inference-cooper
 
 ## Key links
 
-- **Website:** https://inference.coop
-- **AI Chat:** https://chat.inference.coop
-- **Matrix chat:** https://matrix.inference.coop
-- **Member Dashboard:** https://dashboard.inference.coop
-- **Governance forum:** https://forum.inference.coop
-- **Source code:** https://git.inference.coop
-- **Contact:** info@inference.coop
+- **Website:** [inference.coop](https://inference.coop)
+- **AI Chat:** [chat.inference.coop](https://chat.inference.coop)
+- **Matrix chat:** [matrix.inference.coop](https://matrix.inference.coop)
+- **Member Dashboard:** [dashboard.inference.coop](https://dashboard.inference.coop)
+- **Governance forum:** [forum.inference.coop](https://forum.inference.coop)
+- **Source code:** [git.inference.coop](https://git.inference.coop)
+- **Contact:** [info@inference.coop](mailto:info@inference.coop)
 
 ## Governance & legal
 
@@ -34,7 +34,3 @@ funded through our [Open Collective](https://opencollective.com/inference-cooper
 - [Open questions](open-questions.md) — decisions currently up for member discussion.
 - [Terms of Service](terms-of-service.md)
 - [Privacy Policy](privacy-policy.md)
-
----
-
-*This documentation lives in a public git repository. Contributions welcome.*