Stream Feeds - v2 to v3 sync mapping

For CLI commands or routing to another Stream skill, read ../stream/SKILL.md.

Produce the mapping object for an app's v2 -> v3 sync configuration by looking at what the app's v2 data actually contains, rather than at what anyone believes it contains.

One mapping serves both migration paths - the live syncer and the bulk exporter read the same configuration. Getting it right once fixes both; getting it wrong breaks both in the same way.

Workflow

1. Get credentials into the environment