`D417` only triggering when I have no `convention`

### Summary

[`D417`](https://docs.astral.sh/ruff/rules/undocumented-param/) is supposed to be enabled when `convention = google`, but I can only get it to trigger when I remove my `convention` entirely.

https://play.ruff.rs/6daf08f0-a7fc-4e69-81c8-fb82235e5f87

### Version

`ruff 0.9.10 (0dfa810e9 2025-03-07)`

Reproduce the behavior using the linked Ruff Playground example and Ruff 0.9.10, comparing D417 with and without `convention = google`. Trace the D417 implementation and its convention handling, then verify that the Google convention produces the expected diagnostic and add or update regression coverage if the repository identifies a relevant test location.

Written by the indexing model from the issue text.