fix(ci): suppress codecov comments on PRs with no uncovered patch lines (#758)

## Summary

- Change codecov `require_changes` from `true` to `"uncovered_patch"` so
PR comments only appear when the patch itself contains uncovered lines
- `true` (equivalent to `"any_change"`) triggers on indirect coverage
changes (lines whose hit counts shifted even though they weren't
modified), causing spurious comments on PRs that don't touch Go code
(e.g. #757)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: cpcloud

codecov.yml

@@ -12,4 +12,4 @@ coverage:
 
 comment:
   layout: "files"
-  require_changes: true
+  require_changes: "uncovered_patch"