Fix runtime bugs and harden codebase

Clean up repo structure

Update gitignore

Remove unused documentation files

feat: Add agentic RAG, UI overhaul, and codebase improvements

feat: Add GPT-5-Mini query rewriting for better retrieval

docs: Emphasize free tier and Matthew McConaughey use case

docs: Update README - emphasize free tier and Matthew McConaughey use case

docs: Add LinkedIn post template in Paul Graham style

docs: Rewrite README in clear, direct style

fix: Use enumerate index instead of chunk_index for page_idx

fix: Correct method name in vault_monitor (chunk_file -> process_markdown_file)

docs: Enhanced README and .env.example for easy first-time setup

feat: Add incremental vault sync with web UI integration

feat: SOTA web UI with bug fixes