[mocktopus] Swap pip → uv in CI workflow(s)

Replace `python -m pip install --upgrade pip` + `pip install -e .[test]`
with `uv pip install --system -e '.[test]'` in `.github/workflows/ci.yml`.
Adds astral-sh/setup-uv@v8.1.0 (SHA-pinned). Drops the bare pip self-upgrade
per the migration recipe.

Cross-ref: evalops/maestro-internal#1492

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: haasonsaas

.github/workflows/ci.yml

@@ -12,9 +12,8 @@ jobs:
       - uses: actions/setup-python@v5
         with:
           python-version: '3.11'
+      - uses: astral-sh/setup-uv@08807647e7069bb48b6ef5acd8ec9567f424441b # v8.1.0
       - name: Install
-        run: |
-          python -m pip install --upgrade pip
-          pip install -e .[test]
+        run: uv pip install --system -e '.[test]'
       - name: Test
         run: pytest -q