53463b3d8b
Add generate_aliases(), write_aliases(), and redirect_html() to main.rs. For each content item with aliases in frontmatter, writes a minimal HTML redirect stub with meta refresh and canonical link. Alias paths are normalized: bare paths get /index.html appended, .html extensions preserved. Add 2 tests. Test suite: 76 → 78, all passing. Phase 2 complete — all plan items checked off.