ci: get ci working with uv instead of pip

Lots of squashed experimentation heh:

ci: manually specify python version in tests

ci: whoops typo in ruff cmds

ci: specify python versions for uv python install

ci: install python verbosely

ci: try forcing python preference?

ci: try forcing python preference a different way?

ci: try in a venv?

ci: it works, but try without venv

ci: oh maybe we need --preview?

ci: poking it with a stick

ci: it works, add summary to pytest output

ci: fix pytest output

experiment: simulate test failure

Revert "experiment: simulate test failure"

This reverts commit b99ca512f6e61a2a04a1c0636d44018c11019954.

ci: just use default pytest output

cI: attempt again to use uv to install python

cI: attempt again again to use uv to install python

Revert "cI: attempt again again to use uv to install python"

This reverts commit 3cba861c90738081caeeb3eca97b60656ab63929.

Revert "cI: attempt again to use uv to install python"

This reverts commit b30f2277041dc999ed514f6c594c6d6a78f5c810.

.github/workflows/python-tests.yml

@@ -61,7 +61,6 @@ jobs:
     timeout-minutes: 15 # expected run time: 2-6 min, depending on platform
     env:
       PIP_USE_PEP517: '1'
-      # uv requires a venv by default - but for this, we can simply use the system python
       UV_SYSTEM_PYTHON: 1
 
     steps:
@@ -94,9 +93,11 @@ jobs:
           enable-cache: true
           python-version: ${{ matrix.python-version }}
 
-      - name: install python
+      - name: setup python
         if: ${{ steps.changed-files.outputs.python_any_changed == 'true' || inputs.always_run == true }}
-        run: uv python install
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
 
       - name: install dependencies
         if: ${{ steps.changed-files.outputs.python_any_changed == 'true' || inputs.always_run == true }}
@@ -106,4 +107,4 @@ jobs:
 
       - name: run pytest
         if: ${{ steps.changed-files.outputs.python_any_changed == 'true' || inputs.always_run == true }}
-        run: uv run pytest -v
+        run: pytest