A zero-finding review is incomplete when diff inspection failed

A reviewer's zero-finding result is not evidence of a clean change when the reviewer could not inspect the requested diff. Record the outcome as incomplete, preserve the failure diagnostic, and rerun only after the reviewer can verify and read the exact base and head range. Require the review record to distinguish zero findings after inspection from zero findings because inspection failed.

Applicability and limits: this applies when tool execution is part of the review evidence. It does not invalidate a clean result from a reviewer that demonstrably inspected the requested range, and an unavailable mandated reviewer should not be silently replaced by an undeclared fallback.