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.

mkdocs.yml

@@ -1,9 +1,9 @@
 # MkDocs configuration for the member-readable documentation site.
 #
 # The documentation source stays exactly where it is — Markdown files at the
-# repository root (plus maintenance/ and incidents/). This is a *publishing*
-# layer over that source, not an edit of it. docs_dir is the repo root, so no
-# document has to move for the generator to find it.
+# repository root. This is a *publishing* layer over that source, not an edit
+# of it. docs_dir is the repo root, so no document has to move for the
+# generator to find it.
 #
 # Build:  see publishing/build.sh
 # Deploy: see publishing/deploy.sh
@@ -30,6 +30,10 @@ use_directory_urls: true
 
 theme:
   name: material
+  # Theme overrides. Used only to add a "documentation source" link to the
+  # footer on *every* page (overrides/partials/copyright.html) without putting
+  # it in the Markdown sources. No styling is changed here.
+  custom_dir: overrides
   language: en
   # Disable the theme's built-in Google Fonts loader. Without this, Material
   # requests Roboto from fonts.googleapis.com / fonts.gstatic.com.
@@ -76,12 +80,6 @@ nav:
       - Open questions: open-questions.md
       - Terms of Service: terms-of-service.md
       - Privacy Policy: privacy-policy.md
-  - Operator runbook: operator-token-runbook.md
-  - Maintenance:
-      - Chat task models: maintenance/chat-task-models.md
-      - LibreChat sandbox: maintenance/librechat-sandbox.md
-  - Incidents:
-      - 2026-10-02 gateway CVE upgrade: incidents/2026-10-02-gateway-cve-upgrade.md
 
 plugins:
   # Built-in, offline search — the index is a JSON file in the build output.
@@ -113,6 +111,7 @@ extra_css:
 exclude_docs: |
   .git/
   *.sh
+  overrides/
   publishing/README.md
   publishing/requirements.txt