v1.18.0

Fixed

• code reads the configured default model (GEMINI_CODE_CONTEXT_DEFAULT_MODEL, then the credentials profile), as ask and ask_agentic always did; before, a code call without model used latest-pro-thinking whatever the operator configured. A configured default that resolves but cannot reason or think (a flash or lite tier set for cheaper ask calls, or a model without thinking) is replaced by latest-pro-thinking for code, with a warning in the log, a progress line, and configuredModelReplaced in the response, so an audit can tell a fallback from a caller's choice; a configured default that does not resolve at all fails code as it fails ask. A per-call model still wins and is never replaced; an empty model is a schema error. The model descriptions of code and ask_agentic say so. Five tests pin it.