The error return paths in tool_function_bash were returning string literals instead of heap-allocated copies via strdup, causing potential null pointer dereference when callers attempt to free the returned pointer. This fix ensures both "Popen failed!" and "Failed to allocate memory!" error messages are properly duplicated on the heap before being returned.
Implement a new `tool_function_bash` that executes shell commands via `popen` and captures their output into a dynamically allocated buffer. Register the corresponding `tool_description_bash` JSON schema and include it in the `tools_descriptions` array alongside the existing HTTP GET tool. Also change the history file path from `~/.calpaca_history` to `.r_history` and remove the redundant `read_history` call before adding new history entries.
Implement tool calling infrastructure including tools.h with http_fetch function description and execution, message_add_tool_call and message_add_tool_result helpers in messages.h, tool descriptions injection into user messages and chat_json, http header parsing utilities in http.h, curl_get function in http_curl.h, and tool call execution loop in openai_chat that recursively processes tool results.
