feat: share menu, export as Markdown or plain text, chat UI updates

Fix model bleeding past assistant turn with stop sequences

Add Docker + Hugging Face Spaces layout (LLMComparisons-style)

Add context window handling, summarize endpoint, and UI polish

Document sk_klatchat2024 for BrainForge Security (4090 x1-3) vLLM Bearer

Initial Ask Jerry demo: React UI on 3006, FastAPI proxy to vLLM on 8006