Update marimo downstream CI to use uv instead of hatch (#3487)

* Update marimo downstream CI to use uv instead of hatch

Pending on marimo-team/marimo#8510, which
replaces hatch with native uv commands in marimo. Uses `uv add ../
--editable` and a new `scripts/test-narwhals.sh` in marimo instead of
the old hatch-based test invocation.

* Invoke `uv run python`

Author: manzt

.github/workflows/downstream_tests.yml

@@ -78,35 +78,22 @@ jobs:
           cache-dependency-glob: "pyproject.toml"
       - name: clone-marimo
         run: |
-          git clone https://github.com/marimo-team/marimo.git --depth=1
+          # TODO: remove branch pin once https://github.com/marimo-team/marimo/pull/8510 is merged
+          git clone https://github.com/marimo-team/marimo.git --depth=1 --branch=push-kmswtyynuukw
           cd marimo
-          uv venv -p 3.12
           git log
-      - name: install-basics
-        run:
-          uv pip install --upgrade tox virtualenv setuptools hatch
-          "click!=8.3.0" --system
-      - name: install-marimo-dev
+      - name: install-narwhals-dev
         run: |
           cd marimo
-          . .venv/bin/activate
+          uv add ../ --editable
           # Temporary pin until it's addressed upstream.
-          uv pip install "pandas<3"
+          uv add "pandas<3" --group test-optional
           # Temporary pin to get CI green
-          uv pip install "sqlglot<28.7.0"
-          uv pip install -e ".[dev]"
-          which python
-      - name: install-narwhals-dev
-        run: |
-          cd marimo
-          . .venv/bin/activate
-          uv pip uninstall narwhals
-          uv pip install -e ./..
+          uv add "sqlglot<28.7.0" --group test-optional
       - name: show-deps
         run: |
           cd marimo
-          . .venv/bin/activate
-          uv pip freeze
+          uv tree --group test-optional
       - name: Create assets directory, copy over index.html
         continue-on-error: true
         run: |
@@ -117,12 +104,8 @@ jobs:
         if: ${{ matrix.dependencies == 'core,optional' }}
         run: |
           cd marimo
-          . .venv/bin/activate
-          # make sure that we use the .venv when running tests, so that
-          # the local narwhals install is picked up
-          sed -i '/^\[tool.hatch.envs.default\]/a path = ".venv"' pyproject.toml
-          hatch run python -c "import narwhals; print(narwhals.__file__)"
-          hatch run +py=${{ matrix.python-version }} test-optional:test-narwhals
+          uv run --python ${{ matrix.python-version }} python -c "import narwhals; print(narwhals.__file__)"
+          scripts/test-narwhals.sh --python=${{ matrix.python-version }}
         timeout-minutes: 15
 
   scikit-lego: