docs(site): auto-regen hooks, auto sidebars, e2e route check

[ottobolyos]

Summary

Three docs-site changes that together let a contributor clone the repo and run npm install && npm run dev to get a fully rendered, fully browsable site—no manual generation steps, no hand-edited sidebars, no router gaps—plus a Playwright e2e test that fails the build if any route 404s.

Auto-regen on dev and build

predev and prebuild npm hooks now run the docfx + Roslyn reference generators automatically. The contributor's first npm install && npm run dev cycle regenerates docs/api/ and docs/reference/ before the dev server starts, so the local site mirrors what CI builds on every push.

• docs/package.json—adds regen, predev, prebuild scripts.
• .github/workflows/docs.yml—drops the now-redundant explicit generate-api-ref.sh and generate-reference.sh steps (the prebuild hook runs them both before npm run build). The --check drift gate moves ahead of the build so it compares against the committed reference pages rather than the freshly regenerated ones the prebuild hook would otherwise overwrite them with.

Auto-generated sidebars

docs/.vitepress/sidebar.ts derives the /api/ and /reference/ sidebars at config-load time from the generated trees on disk, replacing the hand-maintained entries in config.ts.

• /api/—parses docfx's toc.yml and projects the namespace hierarchy into nested collapsible groups. MTConnect.Devices.DataItems.SampleDataItem lands at MTConnect > Devices > DataItems > SampleDataItem; all ~1800 types are one click from a section landing. Collapsed by default so the viewport stays usable.
• /reference/—lists every .md file under docs/reference/ except index.md (wired in as the Overview entry). Flat alphabetical list—a future generator output appears automatically once generate-reference.sh emits it.

The hand-curated narrative sidebars (/compliance/, /configure/, /concepts/, /cookbook/, /modules/, /wire-formats/, /troubleshooting/, /examples/, /migration/, /development/, /cli/) remain hand-edited; only the two generated trees swap to auto-derivation.

Playwright e2e test for VitePress routes

tests/MTConnect.NET-Docs-Tests/RouteCheckTests.cs builds the docs site, spawns vitepress preview against the built dist/ tree, walks every route the markdown source tree implies in a headless Chromium browser, and asserts no 404s. The test runs as part of the existing dotnet test matrix on the ubuntu-latest leg (windows-latest already excludes Category=E2E). Catches the failure modes a filesystem-level link checker misses—VitePress router misregistration (the trailing-slash-vs-cleanUrls bug from #157 would have failed this test), missing static assets, JS errors in custom theme components.

• tests/MTConnect.NET-Docs-Tests/RouteCheckTests.cs—new NUnit fixture. [OneTimeSetUp] runs npm ci && npm run build when dist/ is missing, installs the Playwright chromium binary, spawns vitepress preview on a free port, then waits for the listener to bind. The route walk allocates one BrowserContext per worker (cap = Math.Min(8, Environment.ProcessorCount)) and reuses it across that worker's share of routes; a companion negative test pins the detector itself by asserting a synthetic unmapped route surfaces as a 404.
• tests/MTConnect.NET-Docs-Tests/MTConnect.NET-Docs-Tests.csproj—adds Microsoft.Playwright 1.60.0.
• .github/workflows/dotnet.yml—adds actions/setup-node (pinned to v6.4.0) on the ubuntu-latest leg so the test fixture's npm ci && npm run build bootstrap can run. Caches docs/package-lock.json, and the Playwright cache key hashes the installed playwright-core package.json so a chromium-revision bump auto-invalidates.