fix(cli): reject ambiguous bare IDs in JSON mode

[ruby-automation]

Summary

• make shared bare-number issue ID expansion output-aware
• reject ambiguous team choices in JSON mode with a stderr diagnostic before any lookup or mutation
• preserve text-mode prompts and full/UUID identifier behavior
• document deterministic bare-number resolution for JSON issue moves

Verification

• mise exec -- mix ci
• 641 app tests passed, including move/unassign JSON regression coverage

Closes EXT-72