Allow "update-issue" safe output

[dsyme]

safe-outputs:
  update-issue:
    status:                             # Optional: presence indicates status can be updated (open/closed)
    target: "*"                         # Optional: target for updates
                                        # "triggering" (default) - only update triggering issue
                                        # "*" - allow updates to any issue (requires issue_number in agent output)
                                        # explicit number - update specific issue number
    title:                              # Optional: presence indicates title can be updated
    body:                               # Optional: presence indicates body can be updated
    max: 3                              # Optional: maximum number of issues to update (default: 1)