Handle conditional request ETag lists

[OskarEichler]

Summary

Handle comma-separated conditional-request ETags, *, and RFC weak comparison for If-None-Match while retaining strong comparison for If-Match.

The current trailing-token extraction ignores earlier list members and wildcards, and treats weak validators as ordinary strong values.

Reproduction

For an asset with ETag abc, If-None-Match: "other", W/"abc" now returns 304 and If-Match: "other", "abc" succeeds. If-Match: W/"abc" remains a strong-comparison miss.

Verification

• Release/current baseline and combined completion candidate: unchanged suite passes 913 tests / 4,109 assertions / 0 failures / 0 errors / 4 skips on Ruby 4.0.6 and 3.2.11.
• Focused external models cover lists, OWS, quoted/unquoted validators, wildcards, weak/strong comparison, GET/HEAD and response ETags on both Rubies.
• Syntax, targeted RuboCop, package parity, isolated gem load and downstream Rails boot pass.

Compatibility

Single current validators retain their behavior. No dependency/version change. Existing tests were not edited under the consumer repository’s no-test-edit policy; focused evidence ran externally. Prepared with AI assistance.