Slice A: coverage fully out of the GUI process; children stop importing the GUI — v0.9.1

[jamesabel]

Summary

Slice A of the crash review: remove the two biggest native-crash surfaces from the GUI process.

1. No coverage.Coverage object is ever constructed in the GUI process. Aggregation already ran in a spawn child after an access violation in python.dll, but CoverageTracker's per-test pass (Coverage(cov_file).load() on its worker thread, once per completed test per recalculation) and compute_per_test_coverage on the run-prep thread still did. CoverageAggregator now takes optional per_test_names and returns a CoverageResult (totals + per-test executed-line counts + union); the tracker and the ordering path derive their fractions from that.
2. Spawn children no longer import pytest-fly's GUI package. Every child re-imports pytest_fly.__main__ → main.py, which imported .gui at module level — so each test process, ProcessMonitor, SystemMonitor, CoverageAggregator and GetTests loaded PySide6 and all eight tabs first (measured 0.58 s and tens of MB commit per child, two children per test), and pytest-fly's own Qt binding sat in the test process before the PUT's tests ran. main.fly_main is now a lazy wrapper and pytest_runner/__init__.py resolves its exports via PEP 562. The PUT is unaffected — if its tests import PySide6/PyQt, they still do exactly as before; only pytest-fly's own side-effect import is gone.

Measured

	before	after
PySide6 in a child's sys.modules	yes	no
pytest_fly.gui.* in a child	yes	no
import pytest_fly.__main__	0.58 s	0.28 s

pytest is still imported by children: interfaces.py builds PyTestFlyExitCode from pytest.ExitCode by design.

Tests

• test_child_returns_per_test_executed_lines — child per-test counts match compute_per_test_coverage, both fraction conventions.
• test_spawn_child_entry_does_not_import_gui — subprocess probe pins the import footprint.
• Full suite: 487 passed. ruff clean; ty unchanged (pre-existing diagnostics only).

Behaviour change

Per-test coverage numbers for the Coverage tab now arrive with the rate-limited aggregation pass rather than being computed on the tracker thread — same values, same cadence as the combined number.

🤖 Generated with Claude Code

https://claude.ai/code/session_01KEZ9TpT9VwBujBq1S3v2Jd

[codecov-commenter]

Codecov Report

❌ Patch coverage is 82.45614% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.08%. Comparing base (89677c0) to head (9642c93).

Files with missing lines	Patch %	Lines
...rc/pytest_fly/pytest_runner/coverage_aggregator.py	78.57%	6 Missing ⚠️
src/pytest_fly/gui/run_tab/control_window.py	50.00%	2 Missing ⚠️
src/pytest_fly/main.py	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #167      +/-   ##
==========================================
- Coverage   86.14%   86.08%   -0.06%     
==========================================
  Files          74       74              
  Lines        6150     6168      +18     
==========================================
+ Hits         5298     5310      +12     
- Misses        852      858       +6     

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