feat: complete overhaul of AI subsystem with multi-agent litellm architecture

- Refactored AI module to use litellm, supporting Anthropic, Google, OpenAI, etc.
- Introduced 'Engineer' (execution) and 'Architect' (strategic) AI agents.
- Added real-time streaming responses and interactive chat mode via 'rich'.
- Added CLI arguments for model/key overrides (--engineer-model, --architect-model).
- Replaced 'openai' with 'litellm' in requirements.txt and setup.cfg.
- Updated nodes.run() to support an 'on_complete' callback for live node-status streaming.
- Fixed an undefined variable bug (config.profiles -> self.profiles) in configfile.py.
- Updated README and docstrings with new AI plugin tool registration API.
- Regenerated HTML documentation using pdoc3.
- Bumped version to 5.0b1 for beta release.

.gitignore

@@ -133,3 +133,12 @@ dmypy.json
 
 #App
 connpy-completion-helper
+
+# Gemini & AI Tools
+.gemini/
+GEMINI.md
+
+# Node.js (used by Gemini CLI or plugins)
+node_modules/
+package-lock.json
+package.json