Documentation site and CI workflows

An mdBook under docs/book: a user guide (getting started, UI tour, sketching, features,
parameters, components and joints, sheet metal, plastic, files, shortcuts, MCP) and a developer
guide (CONTRIBUTING, architecture, command engine, kernel boundary, persistent naming, test
harnesses, and the existing docs/*.md pages). `cargo xtask book` generates the command reference
from `solvecraft-cli commands` and renders the screenshots with `solvecraft-cli snapshot`, then
runs mdbook. .github/workflows/pages.yml publishes the book at /solvecraft/ and the web app at
/solvecraft/app/ (skipped while the repository is private). .github/workflows/ci.yml runs
`cargo xtask ci` on pull requests. README and Help → Documentation link to the book.

Fixes #28
Fixes #8

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/book/book.toml

@@ -0,0 +1,29 @@
+[book]
+title = "SolveCraft"
+description = "An open-source parametric 3D CAD application in pure Rust: user guide and developer guide."
+authors = ["SolveCraft contributors"]
+language = "en"
+src = "src"
+
+[build]
+build-dir = "../../target/book"
+create-missing = false
+
+[output.html]
+git-repository-url = "https://github.com/bherbruck/solvecraft"
+edit-url-template = "https://github.com/bherbruck/solvecraft/edit/main/docs/book/{path}"
+site-url = "/solvecraft/"
+no-section-label = false
+
+[output.html.search]
+enable = true
+
+[output.html.redirect]
+# Pages included from the repository (CONTRIBUTING.md, docs/*.md) keep their repository-relative
+# links; these send them to the right place.
+"/dev/mcp.html" = "../guide/mcp.html"
+"/dev/docs/oracle.html" = "../oracle.html"
+"/dev/README.html" = "https://github.com/bherbruck/solvecraft/blob/main/README.md"
+"/dev/ATTRIBUTION.html" = "https://github.com/bherbruck/solvecraft/blob/main/ATTRIBUTION.md"
+"/dev/AGENTS.html" = "https://github.com/bherbruck/solvecraft/blob/main/AGENTS.md"
+"/dev/ROADMAP.html" = "https://github.com/bherbruck/solvecraft/blob/main/ROADMAP.md"