The generic ValidateIDFormat() used isLikelyHash() which treated
3-character suffixes like "nux" as valid hashes, causing agent IDs
like "nx-nexus-polecat-nux" to extract prefix as "nx-nexus-polecat"
instead of the correct "nx".
Fix: For --type=agent, validate agent ID format first and use
ExtractAgentPrefix() which correctly extracts prefix from the
first hyphen for agent IDs.
Fixes#591
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
87f84c5fa6