FM Phase 5: Proxy mode — memory-augmented /v1/chat/completions #26

Enhance the existing pass-through into a full payload-replacement proxy so OpenClaw (and any OpenAI-compatible agent) gets fading memory + persona for free.

• Parse incoming: extract last user message, tools array, mid-turn tool-call/result messages, model name
• Discard OC history and OC system prompt (Ragger owns conversation state)
• Build Role-2-equivalent payload from Ragger storage, append OC's tools
• Forward upstream, stream back
• Auto-capture user/assistant exchange as memory turn (source: proxy-openclaw)
• Session tracking via X-Session-Id or username+time proximity

Config [proxy]: augment, augment_persona, augment_memory, augment_max_results, augment_min_score, auto_capture, capture_summarize

Files: server.cpp, config.{h,cpp} — est. 200–400 lines