add GitHub Pages wiki site

[kicka5h]

Summary

Adds a static GitHub Pages site under docs/ that serves the existing wiki content as a browsable, single-page wiki using native JavaScript.

Changes

• Create docs/index.html — single-page wiki app with sidebar navigation, hash-based routing, and responsive mobile layout
• Copy all 7 wiki markdown files into docs/wiki/ for static serving
• Use marked.js and highlight.js via CDN for markdown rendering and syntax highlighting
• Support [[Page]] wiki-link syntax, converting them to internal hash links
• Preload all wiki pages in the background after initial page load
• Update .github/workflows/wiki.yml to sync wiki/*.md into docs/wiki/ on push, keeping the Pages site in sync with wiki source

Test plan

• Existing tests pass (pytest tests/ -v)
• New tests added for any new behaviour
• Tested manually with a real stash
• Open docs/index.html locally and verify all 7 wiki pages load and render correctly
• Verify sidebar navigation and hash routing (#Installation, #Commands-Reference, etc.)
• Verify code blocks have syntax highlighting
• Verify [[Page]] wiki-links resolve to internal navigation
• Test responsive layout at mobile widths

Notes for reviewer

• No new Python code or dependencies — this is purely a static HTML/JS/CSS addition
• Markdown rendering uses marked.js and highlight.js from CDN (no vendored files)
• To enable GitHub Pages after merge: Settings > Pages > Deploy from branch main, folder /docs
• The wiki workflow now has a second step that commits synced files back to the repo; this keeps docs/wiki/ up to date automatically when wiki/*.md changes