warn if pdb option is passed on isolated tests

[dyollb]

fixes #34

• If user provides --pdb, the isolation will automatically be disabled and pytest will warn the user to use --no-isolation. Using --no-isolation --pdb should not trigger the warning.

• I could not reproduce the --ff issue

[Copilot]

Pull request overview

This PR addresses issue #34 by automatically disabling isolation when the --pdb flag is used, since the debugger cannot work in subprocesses. The implementation adds a helpful warning that suggests using --no-isolation --pdb explicitly to avoid the warning in the future.

Changes:

• Adds automatic detection of --pdb flag that disables isolation and warns users
• Respects explicit --no-isolation flag to avoid showing redundant warnings
• Adds comprehensive test coverage for the new warning behavior and verifies --ff (failed-first) works with isolated tests

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/pytest_isolated/grouping.py	Adds --pdb detection logic that automatically disables isolation and emits a warning when isolated tests are present
src/pytest_isolated/config.py	Documents that --pdb is not forwarded to subprocesses and isolation is automatically disabled when detected
tests/test_options.py	Adds three new tests: one for --pdb with warning, one for --no-isolation --pdb without warning, and one for --ff functionality

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[pcrespov]

Some thoughts ...

[pcrespov]

thx!