feat(doc): add test section

[paulleseute]

the test section covers the tooling for testing an mcp app: devtools, tunnel, playground, audit. the organizing idea: each tool puts one more actor in the loop. devtools is your app alone (no model, no host), the playground adds a real model, the tunnel adds the real hosts, and the audit (powered by alpic beacon) checks the whole thing headlessly. each page's limitations name what the tool can't test, which is exactly what the next one covers.

tool pages are deliberately lighter than build guides: what problem it solves, setup, a quick feature overview (users will discover the rest by clicking around), then limitations.

the section has a home with a comparison table routing by need (real model / real host / interactive). build got the same treatment: a home page with the four questions an app answers and their core APIs. both homes are wired as group roots, so clicking "Build" or "Test" in the sidebar opens them without adding a tree item.

also:

• build pages now end with an "All done!" card congratulating and handing off to the next chapter (tools -> views -> state -> auth -> test)
• intro concept cards now use the section illustrations and link to the build pages (they were dead links before)
• legacy devtools page and quickstart/test-your-app are superseded by the new section (still in the legacy groups for now)

best reviewed when started locally. make sure your mintlify is up to date so all components are rendered correctly:

mint update
rm -rf ~/.mintlify

Greptile Summary

This PR adds a complete "Test" section to the Skybridge docs covering four tools (DevTools, Tunnel, Playground, Audit), each with a problem statement, setup guide, feature overview, and limitations that hand off to the next tool. It also adds a build/index.mdx landing page with a summary table, wires both Build and Test groups as sidebar group roots, threads "All done!" handoff cards through every build page, and fixes previously dead concept card links in introduction.mdx.

• New test/ section (index + 4 tool pages) and ship.mdx added; docs.json updated with group roots, expanded: true on Build and Test, and a global Lucide icon library setting.
• Build pages gain sequential "All done!" cards linking tools → views → state → auth → test, and get-started pages gain "Go Further" card grids to close previously missing navigation paths.

Confidence Score: 5/5

Documentation-only change with no runtime code; all internal links and image references are consistent with existing and newly added assets.

All changed files are MDX documentation pages and docs.json configuration. New pages are well-formed, internal hrefs match file paths in the repo, new images are added alongside the pages that reference them, and the navigation wiring (group roots, expanded flags, pages vs groups key) is consistent with the Mintlify update the PR description requires. No logic paths, data models, or API contracts are touched.

No files require special attention.

_{Reviews (2): Last reviewed commit: "feat(doc): add ship (#866)" | Re-trigger Greptile}