refuse_provenance validated only agent and session, and only for blank and a
handful of line breaks. It now covers agent, session and tool with the leaf's
Title character rule (an alphanumeric character, no control or line-break
character, no bidi control) inside Short's byte bound. The leaf keeps that rule
private, so a differential test holds the copy to a campaign Title. Restores
the stage doc comment that drifted above SHORT_MAX. Multibyte bound test kills
a chars-count mutant.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
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