Call mypy manually and speedup tests

[timrid]

Call mypy manually instead of using the mypy specific .test files. The .test files was to complicated to use.

Additionaly this speeds up the tests by sharing the mypy_cache folder

[Copilot]

Pull request overview

This pull request modernizes the mypy testing infrastructure by replacing the mypy-specific .test data-driven test format with standard pytest test functions that invoke mypy manually. The change simplifies test authoring and improves test execution speed by sharing a common mypy cache directory across tests.

Changes:

• Upgraded mypy from version 1.15.0 to 1.19.1 with new dependencies (librt, pathspec)
• Replaced mypy data-driven test framework with custom mypy_helper.py module for manual mypy invocation
• Converted 10 .test files to standard Python pytest files with clearer test structure
• Modified CI workflow to run on ubuntu-latest instead of windows-latest and added color output
• Refactored test fixtures to use session-scoped JVM and stub generation for performance

Reviewed changes

Copilot reviewed 25 out of 26 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
uv.lock	Updated mypy to 1.19.1 and added new dependencies (librt 0.8.0, pathspec 1.0.4) with metadata updates
tests/mypy_helper.py	New helper module for running mypy programmatically and validating output against expected markers
tests/conftest.py	Refactored fixtures to use session scope for JVM startup and stub generation; removed mypy test plugin dependency
tests/test_*.py (10 files)	Converted from .test format to standard pytest functions with marker-based assertions
tests/stubtest/test-data/unit/*.test (10 files)	Deleted old data-driven test files
tests/stubtest/README.md	Removed as no longer needed without data-driven tests
tests/test_stubtest.py	Deleted old test suite runner
pyproject.toml	Updated mypy version specification from 1.15.0 to 1.19.1
.github/workflows/python-package.yml	Changed runner from windows-latest to ubuntu-latest and added FORCE_COLOR environment variable

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