ci(starlight): the docs site is built when its files change, informationally

The `starlight` filter of ci-paths.yaml, and a job that runs `npm ci` and `npm run build` in starlight/. It is not
in the needs of `required` yet: the site has not been built by CI before.

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

.github/ci-paths.yaml

@@ -89,3 +89,8 @@ windows:
   - e2e/lib/**
   - e2e/platforms/**
   - wix/**
+
+# the docs site: it does not concern a platform, so a change of it starts the build of the site and nothing else
+starlight:
+  - starlight/**
+  - .github/ci-paths.yaml

.github/dependabot.yml

@@ -10,6 +10,16 @@ updates:
       prefix: chore
       include: scope
 
+  - package-ecosystem: "npm"
+    directory: "/starlight"
+    schedule:
+      interval: "weekly"
+    assignees:
+      - "LGUG2Z"
+    commit-message:
+      prefix: chore
+      include: scope
+
   - package-ecosystem: "cargo"
     directory: "/"
     schedule:

.github/workflows/ci.yaml

@@ -41,6 +41,7 @@ jobs:
       linux: ${{ steps.final.outputs.linux }}
       macos: ${{ steps.final.outputs.macos }}
       windows: ${{ steps.final.outputs.windows }}
+      starlight: ${{ steps.final.outputs.starlight }}
     steps:
       - uses: actions/checkout@v6
         with:
@@ -58,12 +59,14 @@ jobs:
           LINUX: ${{ steps.filter.outputs.linux }}
           MACOS: ${{ steps.filter.outputs.macos }}
           WINDOWS: ${{ steps.filter.outputs.windows }}
+          STARLIGHT: ${{ steps.filter.outputs.starlight }}
         run: |
-          if [ "$ALL" = true ]; then LINUX=true MACOS=true WINDOWS=true; fi
+          if [ "$ALL" = true ]; then LINUX=true MACOS=true WINDOWS=true STARLIGHT=true; fi
           {
             echo "linux=$LINUX"
             echo "macos=$MACOS"
             echo "windows=$WINDOWS"
+            echo "starlight=$STARLIGHT"
           } | tee -a "$GITHUB_OUTPUT"
 
   # ---- stage 0: the pinned tools of the flake, no builds, about two minutes ----
@@ -232,6 +235,26 @@ jobs:
       - run: rustup target add aarch64-apple-darwin
       - run: tools/mac-check.sh
 
+  # the docs site (starlight/), built as it is deployed. Informational: not in the needs of `required`, as the site
+  # has not been built by this workflow before. The reference pages in it are what `just docgen` writes.
+  starlight:
+    needs: [changes]
+    if: ${{ !cancelled() && (github.event_name != 'pull_request' || needs.changes.outputs.starlight == 'true') }}
+    runs-on: ubuntu-24.04
+    timeout-minutes: 15
+    defaults:
+      run:
+        working-directory: starlight
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/setup-node@v6
+        with:
+          node-version: 24
+          cache: npm
+          cache-dependency-path: starlight/package-lock.json
+      - run: npm ci
+      - run: npm run build
+
   # ---- stage 3: tests ----
 
   test: