Enable ruff PTH rule (migrate to pathlib)

[iMicknl]

Summary

• Replace os.path usage with pathlib.Path in test_client.py and mask_fixtures.py
• Remove os import where no longer needed

Test plan

• ruff check . passes
• pytest — 280 tests pass

[Copilot]

Pull request overview

Enables Ruff’s flake8-pathlib (PTH) ruleset and updates a couple of places to use pathlib.Path instead of os.path, aligning the codebase with the new linting expectations.

Changes:

• Enable Ruff PTH rules in pyproject.toml.
• Migrate path handling to pathlib.Path in tests/test_client.py and utils/mask_fixtures.py.
• Remove now-unneeded os/glob imports where applicable.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

File	Description
utils/mask_fixtures.py	Replace glob/os.path.join + open() with Path.glob() + Path.open().
tests/test_client.py	Replace os.path path construction with Path composition for fixture reads.
pyproject.toml	Turn on Ruff PTH lint ruleset.

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[Copilot]

The file header comment mentions ASYNC230, but the file-level # ruff: noqa no longer ignores ASYNC230. Either remove/update the ASYNC230 comment or add ASYNC230 back to the noqa list so the header accurately reflects the lint configuration for this file.

Suggested change

# ASYNC230: Blocking open() is acceptable for reading test fixtures

[Copilot]

Like above, this builds the path using a string containing separators ("fixtures/setup/setup_tahoma_1.json"). Prefer composing the path with separate segments (e.g., "fixtures" / "setup" / "setup_tahoma_1.json") to keep pathlib usage consistent and platform-agnostic.