Introduce conditional compilation via OLLAMA preprocessor flag to switch between OpenAI and Ollama API endpoints, model names, and URLs. Add `build_free` and `run_free` Makefile targets for the Ollama variant. Enhance REPL with `!models` command to list available models, improve error handling in `openai_process_chat_message`, and fix history line addition logic.
Add a new `message_add_object` function in messages.h that appends a json_object to the global message list. Modify openai_chat in openai.h to call this function after processing a chat completion, ensuring the assistant's response object is stored. Also comment out the previous `message_add_tool_call` call to avoid duplicate message storage when tool calls are present, and add a missing `continue` in main.c's repl loop after the dump command to prevent fallthrough.
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.
Add `http_curl.h` providing `curl_post` function using libcurl, update `openai.h` to call `curl_post` instead of `https_post` in both `openai_system` and `openai_chat`, add missing `#ifndef`/`#endif` include guard to `auth.h`, increase HTTP buffer size from 4096 to 1MB, add explicit `(char *)` casts to `malloc`/`realloc` calls in `http.h`, and link `-lcurl` in both `build` and `build_free` Makefile targets.
Add initial project structure including .gitignore for build artifacts,
Makefile with gcc build and run targets, README placeholder, cgi-bin
directory with gpt.py and gpt_template.html, and core C headers for
chat, http, line input, markdown rendering, and messages.
