ci: pin poetry version to 1.8.5 for Python 3.9 compatibility

[kinyoklion]

Requirements

• I have added test coverage for new or changed functionality
• I have followed the repository's pull request submission guidelines
• I have validated my changes against all supported platform versions

Related issues

CI failing on Python 3.9 matrix entries due to Poetry installation error.

Describe the solution you've provided

Moves pipx install poetry==1.8.5 before actions/setup-python so pipx uses the system Python (3.12) instead of the matrix Python (3.9). Poetry 1.8.5's transitive dependencies now require Python 3.10+ (dataclass(slots=True)), so installing via pipx under Python 3.9 fails with TypeError: dataclass() got an unexpected keyword argument 'slots'.

Describe alternatives you've considered

• Pinning Poetry to an older version — would miss bug fixes and features
• Dropping Python 3.9 from the matrix — still a supported version

Additional context

Verified: 3/3 CI passes across all Python versions (3.9–3.13) on both Linux and Windows.

Link to Devin session: https://app.devin.ai/sessions/e40ffc3296dd45648f86ac10c42b6da5
Requested by: @kinyoklion

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Note

Low Risk
CI workflow-only change with no application runtime impact; main risk is misordering steps on future workflow edits.

Overview
Fixes CI failures on Python 3.9 by changing when Poetry is installed in the Linux and Windows matrix jobs.

On both linux and windows, the Install poetry step now runs before actions/setup-python, and Poetry is explicitly pinned to 1.8.5. That way Poetry is installed while the runner still uses a newer system Python, instead of under the matrix Python 3.9 where Poetry 1.8.5’s dependencies can fail (e.g. dataclass(slots=True)).

Test and build steps still use the matrix Python after setup; only the Poetry install order and version pin change.

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[keelerm84]

Instead of installing poetry through pipx directly, you should be able to use the abatilo/actions-poetry directly.

      - name: Install poetry
        uses: abatilo/actions-poetry@7b6d33e44b4f08d7021a1dee3c044e9c253d6439
        with:
          poetry-version: ${{ matrix.poetry-version }}

Also heads up but I think Jason is switching all the python stuff over to uv.

[devin-ai-integration]

Good call — updated to use abatilo/actions-poetry with poetry-version: "1.8.5", still placed before setup-python so pipx uses the system Python instead of the matrix Python (3.9). Pushed in eeabcd7.