Tighten test assertions: drop dead asserts, relax cycle-rotation check, capture warnings, exercise union arm

[lesnik512]

Summary

Five test-quality improvements from the 2026-06-05 bug-hunt audit (nice-to-have items #5, #6, #9, #10, #14). No source code changes.

• Injecting factory itself #5 `test_container_resolve_missing_provider`: Dropped `assert app_container.resolve(str) is None` — the call raises before the comparison runs, so the assert was dead code that would have hidden a regression where `resolve` started returning None instead of raising.
• Add Litestar integration #6 `test_func_with_union_factory`: Replaced `assert instance1` (passes for any non-empty string) with `assert instance1 == str(SimpleCreator(dep1='original'))`. Now actually exercises which arm of the `SimpleCreator | int` union was selected — changing the creator to return `'X'` would correctly fail this test.
• add LiteStar integration #9 `test_func_with_broken_annotation`: Moved Factory construction inside the test body, wrapped in `pytest.warns(UserWarning, match='Failed to resolve type hints')`. Now verifies the `UserWarning` from `parse_creator`'s `NameError` branch is actually emitted — removing the `warnings.warn(...)` call in `types_parser` would now fail this test.
• Add LiteStar Example #10 `test_validate_detects_cycle`: Replaced `assert cycle_path == ['CycleA', 'CycleB', 'CycleA']` (depends on Group declaration order) with rotation-independent checks: `cycle[0] == cycle[-1]` and `set(cycle) == {'CycleA', 'CycleB'}`. Swapping the declaration order of `a` and `b` in `CycleGroup` no longer breaks the test.
• implement factories injecting #14 `test_alias_resolve_provider`: Deleted. The sibling `test_alias_delegates_to_source` already performs the load-bearing `concrete is abstract` identity check; this test only asserted `isinstance`, which would pass even with `Alias.resolve` broken to construct a fresh instance.

Also dropped the now-unused module-level `func_with_broken_annotation` Factory registration in `MyGroup` since #9 moved it into the test body.

Test plan

• Updated tests pass; deleted test gone; full suite green (146 passed).
• 100% coverage maintained.
• `just lint-ci` green.

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