Allow IBKR configured image-only staging

[Pigbibi]

Summary

• Let configured targets stage an image without environment/Secret synchronization when explicitly dispatched with sync_env=false.
• Preserve the existing defaults and repository authorization flags.
• Document the exact-target image-only path for notification releases.

Verification

• Workflow shell contract check passed.
• YAML parse and diff check passed.
• CI is the final release check before merging.