feat(docs): create sukr documentation site with fixes

Self-documenting docs site built with sukr itself (dogfooding):

Core changes:
- Rename package from nrd-sh to sukr
- Move personal site to sites/nrd.sh/
- Update AGENTS.md and README.md

Documentation site (docs/):
- Add site.toml with sukr.io base URL
- Create docs-specific templates with sidebar navigation
- Add dark theme CSS with syntax highlighting colors
- Document all features: templates, sections, syntax highlighting,
  mermaid diagrams, and LaTeX math rendering

Bug fixes:
- Render individual pages for all sections (not just blog type)
- Add #[source] error chaining for Tera template errors
- Print full error chain in main() for better debugging

treefmt.toml

@@ -19,7 +19,7 @@ options  = ["fmt", "-o", "align_entries=true", "-o", "reorder_keys=true"]
 [formatter.prettier]
 command  = "prettier"
 excludes = ["*/sources.json"]
-includes = ["*.json", "*.md", "*.yaml", "*.yml", "*.html"]
+includes = ["*.json", "*.md", "*.yaml", "*.yml"]
 options  = ["--write"]
 
 [formatter.rustfmt]