ci(docs): bump runner Node from 20 to 22 for Astro 6 floor

Astro 6 raised its Node floor to `>=22.12` (`engines.node` in the
astro@6.x manifest, EBADENGINE warning at install time + a hard
"Node.js v20 is not supported by Astro!" abort at `astro build`).
Bumping the docs-build / docs-screenshots-build / docs-screenshots-capture
runners to Node 22 unblocks the paired astro@^5 → ^6 + @astrojs/starlight@^0.30
→ ^0.39 dependency bump in this PR.

The web panel's runtime stack is unaffected (PHP 8.5; the only
client-side TS check runs over `web/scripts/` and stays on Node 20
via `ts-check.yml`).

Author: rumblefrog

.github/workflows/docs-build.yml

@@ -35,7 +35,11 @@ jobs:
       - name: Setup Node
         uses: actions/setup-node@v4
         with:
-          node-version: '20'
+          # Astro 6 requires Node >=22.12; 20 trips an EBADENGINE on `npm
+          # ci` and a hard "Node.js v20 is not supported by Astro!" on
+          # `astro build`. Bumped together with the docs astro+starlight
+          # group bump (#1346).
+          node-version: '22'
           cache: 'npm'
           cache-dependency-path: docs/package-lock.json
 

.github/workflows/docs-screenshots-build.yml

@@ -43,7 +43,10 @@ jobs:
       - name: Setup Node
         uses: actions/setup-node@v4
         with:
-          node-version: '20'
+          # Astro 6 requires Node >=22.12; mirrors the bump in
+          # docs-build.yml that landed with the docs astro+starlight
+          # group bump (#1346).
+          node-version: '22'
           cache: 'npm'
           cache-dependency-path: docs/package-lock.json
 

.github/workflows/docs-screenshots-capture.yml

@@ -143,7 +143,10 @@ jobs:
       - name: Setup Node
         uses: actions/setup-node@v4
         with:
-          node-version: '20'
+          # Astro 6 requires Node >=22.12; mirrors the bump in
+          # docs-build.yml that landed with the docs astro+starlight
+          # group bump (#1346).
+          node-version: '22'
           cache: 'npm'
           cache-dependency-path: trusted/docs/package-lock.json