Repeat graphviz errors on subsequent builds

[Mirochill]

Summary

• mark documents with Graphviz render failures for re-read on the next build
• fall back to the current document name for Graphviz callers that do not pass docname explicitly
• add a regression test showing the warning is emitted again on an incremental rebuild

This intentionally addresses the repeated-warning part of #14361 only; stale generated images are a separate concern.

Validation

• Not run locally
• static validation: git diff --check

Refs #14361