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/test-ecosystem.yml

@@ -0,0 +1,65 @@
+on:
+  workflow_call:
+    inputs:
+      sha:
+        required: true
+        type: string
+
+permissions: {}
+
+jobs:
+  ecosystem-test:
+    name: "${{ matrix.repo }}"
+    timeout-minutes: 10
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        include:
+          - repo: "prefecthq/prefect"
+            ref: "7f25bbdf45fc81cca6dc23fb6a7377d436b70c83"
+            commands:
+              - "uv venv"
+              - "uv pip install -e '.[dev]'"
+            python: "3.9"
+          - repo: "pallets/flask"
+            ref: "b78b5a210bde49e7e04b62a2a4f453ca10e0048c"
+            commands:
+              - "uv venv"
+              - "uv pip install -r requirements/dev.txt"
+            python: "3.12"
+          - repo: "pydantic/pydantic-core"
+            ref: "d03bf4a01ca3b378cc8590bd481f307e82115bc6"
+            commands:
+              - "uv sync --group all"
+              - "uv lock --upgrade"
+            python: "3.12"
+      fail-fast: false
+    steps:
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+        with:
+          repository: ${{ matrix.repo }}
+          ref: ${{ matrix.ref }}
+          persist-credentials: false
+
+      - uses: actions/setup-python@83679a892e2d95755f2dac6acb0bfd1e9ac5d548 # v6.1.0
+        with:
+          python-version: ${{ matrix.python }}
+
+      - name: "Download binary"
+        uses: actions/download-artifact@d3f86a106a0bac45b974a628896c90dbdf5c8093 # v4.3.0
+        with:
+          name: uv-linux-libc-${{ inputs.sha }}
+
+      - name: "Prepare binary"
+        run: chmod +x ./uv
+
+      - name: "Test"
+        run: |
+          echo '${{ toJSON(matrix.commands) }}' | jq -r '.[]' | while read cmd; do
+            echo "+ $cmd" >&2
+            if [[ $cmd == uv* ]]; then
+              ./$cmd
+            else
+              $cmd
+            fi
+          done