refactor: clean up codebase and streamline documentation

- Remove debug prints from vendor routing (interface.py)
- Simplify vendor fallback to only handle rate limits
- Reorder CLI provider menu: OpenAI, Google, Anthropic, xAI, OpenRouter, Ollama
- Remove dead files: local.py, reddit_utils.py, openai.py, google.py, googlenews_utils.py, yfin_utils.py

.env.example

@@ -1,2 +1,5 @@
-ALPHA_VANTAGE_API_KEY=alpha_vantage_api_key_placeholder
-OPENAI_API_KEY=openai_api_key_placeholder
+# LLM Providers (set the one you use)
+OPENAI_API_KEY=
+GOOGLE_API_KEY=
+ANTHROPIC_API_KEY=
+OPENROUTER_API_KEY=