If the user's uv.lock contains a version that is known to be malicious, then we should reject its installation.

This is slightly different from what uv audit does -- uv audit principally checks from known vulnerabilities, not malware or compromised packages. The latter is reported via a distinct "stream" on OSV (MAL- reports).

I need to think a bit more about the design here/implications.

• Support filtering by malware (MAL-) in the OSV client: Enable filtering OSV results for malware #18934
• Fetch MAL- entries during lockfile installation and reject the install if we have any: Reject locked malware installations #18936
• Cache MAL- lookups: Cache positive OSV hits #19038