build: finish cross-platform release tooling

include/cst_agent.h

@@ -278,6 +278,8 @@ int cst_llm_list_models(const char *api_base, const char *api_key,
 char *cst_llm_build_body(const cst_llm_request_t *req);
 /* Reset the CST_RECORD_SSE / CST_REPLAY_SSE sequence counter. */
 void cst_llm_trace_reset(void);
+/* Set CURLOPT_CAINFO on a CURL * when a CA bundle file is known. */
+void cst_curl_apply_ca(void *curl);
 
 /* on_permission answers */
 #define CST_PERM_DENY 0