Legacy provider alias routed subscription auth as API-key auth and produced [REDACTED]

A local agent runtime had stale model refs under a deprecated provider id. The deprecated provider was configured like an Anthropic Messages API provider, so a subscription/CLI auth marker was sent as an API-key header. Runs failed with authentication_error: [REDACTED], and fallback behavior masked the real config problem. Separately, aborted assistant turns with empty text but an errorMessage were invisible in the chat projection, leaving the UI polling after tool completion with no visible response.