refactor!: Remove explicit pyarrow dependency

[Oliver Borchert (borchero)]

Motivation

With #385, there is no need for pyarrow anymore.

The positive LoC in this PR stem merely from the fact that we can "demote" pyarrow to a non-optional test dependency which results in it being installed in more environments.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (6ec3629) to head (841c771).

Additional details and impacted files

@@             Coverage Diff              @@
##           pycapsuel      #384    +/-   ##
============================================
  Coverage     100.00%   100.00%            
============================================
  Files             56        56            
  Lines           3522      3416   -106     
============================================
- Hits            3522      3416   -106     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Copilot]

Pull request overview

This PR removes the library’s explicit PyArrow integration surface (Schema/Column helpers) and shifts PyArrow-related schema conversion to the Arrow PyCapsule interface introduced in #385, while keeping pyarrow available as a test dependency via Pixi.

Changes:

• Removed Schema.to_pyarrow_schema and all Column.pyarrow_* helpers, along with the _compat.pa shim.
• Updated tests and docs to stop referencing to_pyarrow_schema, and consolidated PyArrow schema checks around pyarrow.schema(SchemaClass).
• Adjusted dependency configuration: removed the pyarrow optional extra and added pyarrow to Pixi’s feature.test dependencies.

Reviewed changes

Copilot reviewed 25 out of 26 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/columns/test_pyarrow.py	Removed PyArrow-specific schema conversion test suite tied to the deleted API.
tests/columns/test_arrow_pycapsule.py	Switched to direct pyarrow import and removed optional-skipping in favor of always-on test dependency.
tests/column_types/test_object.py	Removed test asserting Object.pyarrow_dtype behavior (API removed).
pyproject.toml	Removed pyarrow optional extra and updated mypy override module list.
pixi.toml	Moved pyarrow from optionals to the test feature dependencies.
docs/index.md	Updated external-tool integration wording to remove direct PyArrow mention.
docs/api/schema/conversion.rst	Removed Schema.to_pyarrow_schema from conversion API docs.
docs/_templates/classes/column.rst	Updated Column API doc exclusions to drop PyArrow members.
dataframely/schema.py	Removed to_pyarrow_schema classmethod and PyArrow compat import.
dataframely/columns/_base.py	Removed abstract pyarrow_dtype and pyarrow_field API from the Column base class.
dataframely/_compat.py	Removed the optional import shim for pyarrow as pa and stopped exporting pa.
dataframely/columns/any.py	Removed PyArrow field/dtype helpers from Any.
dataframely/columns/array.py	Removed PyArrow dtype construction helpers from Array.
dataframely/columns/binary.py	Removed pyarrow_dtype from Binary.
dataframely/columns/bool.py	Removed pyarrow_dtype from Bool.
dataframely/columns/categorical.py	Removed pyarrow_dtype from Categorical.
dataframely/columns/datetime.py	Removed PyArrow dtype mappings from date/time/datetime/duration columns.
dataframely/columns/decimal.py	Removed pyarrow_dtype from Decimal.
dataframely/columns/enum.py	Removed pyarrow_dtype dictionary encoding logic from Enum.
dataframely/columns/float.py	Removed pyarrow_dtype from float columns.
dataframely/columns/integer.py	Removed pyarrow_dtype from integer columns.
dataframely/columns/list.py	Removed pyarrow_dtype from List.
dataframely/columns/object.py	Removed pyarrow_dtype from Object.
dataframely/columns/string.py	Removed pyarrow_dtype from String.
dataframely/columns/struct.py	Removed pyarrow_dtype from Struct.