docs: add all missing pages to mkdocs nav and fix absolute link

- Add 32 pages to nav: architecture (9), modules (1), migrations (1),
  testing (3), proposals (8), archive (11)
- Fix absolute link in jinja-macros.md that mkdocs couldn't validate
- Exclude mkdocs.yml from check-yaml hook (uses !!python/name tags)
- Result: mkdocs build with zero warnings

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.pre-commit-config.yaml

@@ -23,6 +23,7 @@ repos:
       - id: trailing-whitespace
       - id: end-of-file-fixer
       - id: check-yaml
+        exclude: mkdocs.yml  # Uses Python tags (!!python/name) unsupported by basic YAML checker
       - id: check-added-large-files
         args: ['--maxkb=1000']
       - id: check-json