Improve test coverage and refactor visitor.rs

[MatthewMckee4]

Summary

• Refactor try_process_imported_symbol in visitor.rs to use ? via resolve_imported_fixture(), replacing 15 let ... else { return } patterns
• Extract is_generator() helper to deduplicate generator detection logic
• Add 10 new integration tests covering previously untested CLI flags and feature combinations

Refactoring

• try_process_imported_symbol now delegates to resolve_imported_fixture() -> Option<()> which uses ? for all fallible steps
• is_generator() extracted as a standalone function, used by both process_fixture_function and resolve_imported_fixture

New tests

• --fail-fast stops after first failure, works across modules
• --dry-run with nested package structure
• -s (show Python output) flag
• --retry flag for flaky tests
• --output-format=concise with test failures and discovery errors
• --durations with skipped tests (verifies skipped tests appear in durations)
• --last-failed with multiple files and after fixing a test
• @expect_fail combined with @parametrize (both pytest and karva)

Test plan

• just test — all 716 tests pass
• uvx prek run -a — all checks pass

🤖 Generated with Claude Code

[codspeed-hq]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 1 untouched benchmark

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_{Comparing improve-coverage-round-2 (a1857e0) with main (123b682)}

[codecov]

Codecov Report

❌ Patch coverage is 89.74359% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...rates/karva_test_semantic/src/discovery/visitor.rs	89.74%	4 Missing ⚠️

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