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.
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.
