Function resolveOperationRef

Resolve a route's operationRef to an EXISTING operation. Supports the three operation loci:

• #/paths/<pathTemplate>/requests/<name> (a pathItem request — the common case)
• #/webhooks/<name> (an incoming webhook operation)
• #/x-suluk-jobs/<name> (a non-HTTP job, C025) Returns null when the ref dangles (the resolve-lint failure — Conin's MCP-only run_core_primitive).