Implement claiming for queue messages using beads-native approach:
- Add claim_pattern field to QueueFields for eligibility checking
- Add MatchClaimPattern function for pattern matching (wildcards supported)
- Add FindEligibleQueues to find all queues an agent can claim from
- Rewrite runMailClaim to use beads-native queue lookup
- Support optional queue argument (claim from any eligible if not specified)
- Use claimed-by/claimed-at labels instead of changing assignee
- Update runMailRelease to work with new claiming approach
- Add comprehensive tests for pattern matching and validation
Queue messages are now claimed via labels:
- claimed-by: <agent-identity>
- claimed-at: <RFC3339 timestamp>
Messages with queue:<name> label but no claimed-by are unclaimed.
Closes gt-xfqh1e.11
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
2ffc8e8712