chore: consolidate install, fix CLI portability, normalize LLM responses

- Point requirements.txt to pyproject.toml as single source of truth
- Resolve welcome.txt path relative to module for CLI portability
- Include cli/static files in package build
- Extract shared normalize_content for OpenAI Responses API and
  Gemini 3 list-format responses into base_client.py
- Update README install and CLI usage instructions

requirements.txt

@@ -1,21 +1 @@
-typing-extensions
-langchain-core
-langchain-openai
-langchain-experimental
-pandas
-yfinance
-stockstats
-langgraph
-rank-bm25
-setuptools
-backtrader
-parsel
-requests
-tqdm
-pytz
-redis
-rich
-typer
-questionary
-langchain_anthropic
-langchain-google-genai
+.