- coerce_seed("") returns None, not ValueError; move "" out of the
invalid-values parametrize and give it its own explicit assertion
- strip_think_content tests used \\n (literal backslash-n) instead of
real newlines; .strip() cannot remove backslash or 'n' so the dangling-
tag test always failed. Replace with actual \n to match real LLM output.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
