chore: audit follow-ups from plan review

Four small fixes surfaced by a side-by-side plan-vs-shipped pass:

- README.md: adds the Template Catalog section the plan called out —
  links to the live site URL, the install flows (web / file / Finder),
  and templates/CONTRIBUTING.md for authors. Placed right before the
  existing Contributing section, with a catalog-specific cross-link at
  the end of that section too.
- CLAUDE.md: adds the Template Catalog section so future agent sessions
  know the regenerator pipeline exists, how it relates to release.sh +
  wiki.sh, and what the schema-sync rule is when DashboardWidget or
  ProjectTemplateManifest change.
- scarf/scarfTests/ProjectTemplateTests.swift: fixes the stale
  ProjectTemplateExampleTemplateTests docstring still referencing
  `examples/templates/` (the example moved to `templates/awizemann/`
  in 70f7cea).
- .github/workflows/validate-template-pr.yml: untangles the self-
  contradictory Python-version comment. The validator is 3.9+
  compatible; CI uses 3.11 for faster runner caching. Same stdlib
  surface, same code paths — just clearer about why.

All tests still green: 22 Swift tests in 7 suites, 16 Python tests,
catalog check passes on the site-status-checker example.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/validate-template-pr.yml

@@ -36,9 +36,10 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          # Stdlib-only script; any modern Python works. 3.9 matches the
-          # system Python on current macOS so we exercise the same code
-          # path maintainers hit locally.
+          # The validator is stdlib-only and tested against 3.9+ (the
+          # system Python on current macOS, what most maintainers run
+          # locally). CI uses 3.11 for faster cold-cache times on
+          # GitHub Actions runners — same stdlib APIs, same code paths.
           python-version: '3.11'
 
       - name: Run validator unit tests