split Deploy into a hub + 3 sub-pages; inline comments over annotations

The Deploy page got long and the code annotations rendered inconsistently
(some as (n) numbers, some as clickable +, and a marker on a fully-commented
line made that line vanish). Fix both:

- Deploy is now a HUB (docs/deploy/index.md): the intro + collision rule +
  central-deploy note, then card links to three focused sub-pages. Deploy
  stays the single global-nav entry; sub-pages are not_in_nav, reached from
  the hub cards.
  - deploy/compose.md — compose convention, storage tiers, how deploy fills
    it in, subprocess/browser knobs, checklist
  - deploy/dockerfile.md — services-account image, COPY, layer caching, uv
  - deploy/secrets.md — keeping secrets out of the image
- Replace code annotations with INLINE COMMENTS on the compose/Dockerfile
  examples: everything visible at once, no + to click, and the commented
  MOUNTS_DIR line no longer disappears.
- Update inbound links (index card, standards, workflow, environments) to
  deploy/ and deploy/compose.md; nav Deploy -> deploy/index.md with
  not_in_nav for the sub-pages.

Verified in-browser: hub cards link correctly, sub-pages render with visible
inline comments (0 annotation markers), left nav shows only Deploy;
mkdocs build --strict clean (validates not_in_nav + all cross-links).

Signed-off-by: disqualifier <dev@disqualifier.me>

mkdocs.yml

@@ -55,4 +55,10 @@ nav:
   - Standards: standards.md
   - Workflow: workflow.md
   - Virtual environments: environments.md
-  - Deploy: deploy.md
+  - Deploy: deploy/index.md
+
+# Deploy sub-pages are reached from the Deploy hub's cards, not the global nav.
+not_in_nav: |
+  /deploy/compose.md
+  /deploy/dockerfile.md
+  /deploy/secrets.md