Add comprehensive tests for validateOpenIssuesForSync():
- ModeNone: validation skipped when config is "none"
- ModeEmpty: validation skipped for empty config (backwards compat)
- ModeWarn: sync proceeds with warnings for invalid issues
- ModeError: sync blocked with error for invalid issues
- NoWarnings: valid issues pass validation
- SkipsClosedIssues: closed issues not validated
- ChoreHasNoRequirements: chore type has no required sections
The pre-sync validation hook was already implemented as part of bd-t7jq.
This commit adds the missing test coverage.
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>