feat: add LLM-wiki pattern — persistent agent context in _context/wiki/

[Lang-Akshay]

What

Adds the _context/wiki/ folder and wires it into AGENTS.md — the LLM-wiki pattern for giving agents persistent project context without flooding every prompt with a wall of text.

Why

Based on the BOB AI training insight: agents perform better when they have a lightweight, linked knowledge base they consult selectively (check the index, follow only relevant links) rather than receiving the full context every turn.

Structure

contextforge-data-plane/
├── _context/
│   └── wiki/
│       ├── index.md         ← quick-orientation table + links; read this first
│       ├── project.md       ← what/why/who, system topology, active work
│       └── preferences.md   ← working standards, code style, logging rules, AI interaction
└── AGENTS.md                ← instructs agents: check index before acting, offer to update after

How agents use it

1. Start of task — check _context/wiki/index.md, follow links only when relevant.
2. End of task — if the task produced durable knowledge, offer to update the wiki and wait for approval.

This keeps the wiki alive and accurate without burdening every session with full-file reads.

[lucarlig]

We need an unique source of truth. We already have the book and the Summary.md please optimize that for AI rather than writing something new from scratch