chore: clean up repo for release — gitignore internal files, fix site issues

Repo cleanup:
- Gitignore: .claude/, .stitch/, ai/, docs/superpowers/, plans/,
  marketing/variants/, node_modules/, .astro/
- Remove tracked internal files (plans, specs, design explorations)
- These files stay on disk for local reference but are not in the public repo

Site fixes (from frontend review):
- JS-disabled fallback (.js class on html, data-animate only hides with JS)
- View Transition script lifecycle (Nav/Sidebar/TOC use is:inline + astro:after-swap)
- OG/Twitter meta tags, canonical URL
- @astrojs/sitemap + robots.txt
- Skip-to-content link for keyboard a11y
- Comparison table mobile scroll affordance
- Favicon (SVG)
- Prose links underlined by default (WCAG 1.4.1)
- Reduced-motion: scroll-behavior: auto
- Features section h2 heading added
- Removed unused @astrojs/cloudflare dependency

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: michaelmcnees

.gitignore

@@ -40,3 +40,17 @@ coverage.html
 
 # Worktrees
 .worktrees/
+
+# Claude Code / AI tooling
+.claude/
+ai/
+.stitch/
+
+# Internal development process (plans, specs, design exploration)
+docs/superpowers/
+plans/
+marketing/variants/
+
+# Node (site/)
+node_modules/
+.astro/