fix: ignore URL suffixes when scoring file extensions - #2405

Summary

ContentTypeScorer({'.pdf$': 1.0}) gives report.pdf?version=1.2 a zero score because extension lookup uses the last dot in the whole URL. Dotted fragments and path parameters have the same effect; dots in parent directories can also score an extensionless final segment incorrectly.

Bound extension lookup to the final slash-delimited segment before its suffixes. Keep regex fallback on the original URL and preserve weights/cache behavior. This is not a general URL-parser change; authority-only URL behavior is unchanged.

Validation

• Eleven new assertion-based public-score tests: seven failures on the original code, all passing with the fix. Fourteen tests pass in the focused run; some existing scorer coverage is diagnostic-only.
• No network access. New tests pass Black; existing production formatting debt is left unchanged. Full suite not run.
• Hosted workflows may require maintainer approval; no hosted pass is claimed.

AI assistance was used for implementation, testing, and review.