Define the catalog and client-version compatibility facts

[iam-brain]

Question

What catalog and client-version facts constrain a safe Ultra implementation for Sol and Terra in this repository?

Investigate and record:

• which live and GitHub fallback fields must be parsed and retained, including multi_agent_version, supported-effort descriptions, minimal_client_version, visibility, and API support;
• whether the current account-scoped catalog endpoint differs from the checked-in upstream snapshot for Ultra-relevant fields;
• how client-version headers influence model/effort visibility and whether the current asynchronous refresh creates a cold-start race;
• the implications of current 0.116.0 fallback constants versus Sol/Terra's advertised minimum;
• stale-cache and account-scope transitions;
• custom-model aliases and effort-suffix matching;
• which compatibility behavior is representable from authoritative metadata, in line with the repository's no-hypothetical-fallback invariant.

The resolution should state verified constraints and candidate compatibility fixes, but leave product visibility and architecture choices to their decision tickets.