docs: Material for MkDocs site with GitHub Pages deploy

[OsherElhadad]

What

A public documentation website for context-guru, in the style of adk.dev — built with Material for MkDocs, reusing the existing Markdown docs in place, and deployed to GitHub Pages via a new Actions workflow.

Highlights

• Marketing homepage (custom overrides/home.html): hero, copyable run command, feature cards for the three guarantees + integration modes, a before→after compaction demo, and a benchmark highlight.
• ADK-style nav: Get Started, Concepts, Components (overview + 13 per-component pages + the DSL engine), How-to Guides, Examples, Benchmarks, Reference, Community.
• Visualizations: native Mermaid architecture diagrams, MathJax for the phi_evict Φ formula, and an interactive Chart.js benchmark chart on the Results page (real SWE-bench numbers).
• Claude Code integration: how-to/use-with-claude-code.md (one-env-var setup) + scripts/with-guru.sh helper; fixed the stale scripts/cc-demo.sh to the current proxy interface.
• Doc/code drift fixed: documented the toon component (was missing from components.md).
• Deploy: .github/workflows/docs.yaml builds with mkdocs build --strict on PRs and deploys Pages from main; decoupled from the Go CI.

Preview locally

pip install -r requirements-docs.txt
mkdocs serve

Verified

• mkdocs build --strict passes with zero warnings.
• Deterministic components sanity-checked: format+toon via POST /compact on the committed sample is byte-identical to the expected output.

Notes for merge

• Enable GitHub Pages with Source = "GitHub Actions" in repo settings so the deploy job can publish.
• The benchmark chart data is inlined in docs/javascripts/charts.js (marked with a ponytail: comment) rather than auto-synced to the results CSV.
• IBM Bob integration lands in a follow-up PR (needs a small proxy feature ported from winnow).