Split up ci.yml (#17388)

This file is too big for an LLM context window and several contributors
have complained about it being too scary to touch.

This also gets us collapsible sections in the UI.

I renamed some jobs for clarity in the meantime. And added a meta-job
for required checks passing so we can avoid churn in our "Settings" when
we change job names.

Note this was entirely refactored by Claude.

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

.github/workflows/check-docs.yml

@@ -0,0 +1,42 @@
+on:
+  workflow_call:
+
+permissions: {}
+
+jobs:
+  docs:
+    timeout-minutes: 10
+    name: "mkdocs"
+    runs-on: ubuntu-latest
+    env:
+      MKDOCS_INSIDERS_SSH_KEY_EXISTS: ${{ secrets.MKDOCS_INSIDERS_SSH_KEY != '' }}
+    steps:
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+        with:
+          fetch-depth: 0
+          persist-credentials: false
+      - uses: astral-sh/setup-uv@681c641aba71e4a1c380be3ab5e12ad51f415867 # v7.1.6
+        with:
+          version: "0.9.24"
+
+      - uses: actions/setup-python@83679a892e2d95755f2dac6acb0bfd1e9ac5d548 # v6.1.0
+      - uses: Swatinem/rust-cache@779680da715d629ac1d338a641029a2f4372abb5 # v2.8.2
+        with:
+          save-if: ${{ github.ref == 'refs/heads/main' }}
+      - name: "Generate reference documentation"
+        run: |
+          cargo dev generate-options-reference
+          cargo dev generate-cli-reference
+          cargo dev generate-env-vars-reference
+      - name: "Add SSH key"
+        if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS == 'true' }}
+        uses: webfactory/ssh-agent@a6f90b1f127823b31d4d4a8d96047790581349bd # v0.9.1
+        with:
+          ssh-private-key: ${{ secrets.MKDOCS_INSIDERS_SSH_KEY }}
+
+      - name: "Build docs (public)"
+        run: uvx --with-requirements docs/requirements.txt mkdocs build --strict -f mkdocs.public.yml
+
+      - name: "Build docs (insiders)"
+        if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS == 'true' }}
+        run: uvx --with-requirements docs/requirements-insiders.txt mkdocs build --strict -f mkdocs.insiders.yml