[Guide] Agent OS Architecture Overview

Summary

Add a new top-level guide agentos/ArchitectureOverview to the learning portal that provides a comprehensive architectural map of the Neo.mjs Agent OS.

Motivation

The "Agent OS & Conversational UIs" section currently has guides for individual MCP servers (Neural Link, Knowledge Base, Memory Core, GitHub Workflow, Code Execution) and Strategic Workflows, but no entry point that ties the entire system together. A developer or contributor encountering the Agent OS for the first time has no single document that explains:

1. How the frontend runtime engine and the Agent OS relate as "two hemispheres" of a single platform
2. The cognitive loop (Perceive → Reason → Act → Reflect)
3. The DreamService REM pipeline (6 phases including deterministic gap inference)
4. The closed feedback loop that makes the system self-improving
5. The Neural Link bridge between Node.js agents and the live browser application

Proposed Changes

1. New Guide: learn/guides/agentos/ArchitectureOverview.md

• Adapted from the architectural artifact created in session 70334eab
• Sections: Two Hemispheres, Runtime Engine, Agent OS, Neural Link Bridge, Dream Pipeline, The Closed Loop, Structural Inventory
• Remove internal meta-commentary (Gemini comparison section) — reorient for external audience
• Include Mermaid diagrams throughout

2. Update: learn/tree.json

• Add entry "Architecture Overview" as the first child of "AgentOS" (parentId: "AgentOS", id: "agentos/ArchitectureOverview")
• Position before "Strategic Workflows" to serve as the conceptual entry point

Acceptance Criteria

• Guide renders correctly in the learning portal with all Mermaid diagrams
• tree.json updated and the guide appears first under "Agent OS & Conversational UIs"
• Knowledge Base re-synced (manage_knowledge_base sync) so the guide is discoverable via ask_knowledge_base

A2A Context

• Origin Session ID: 70334eab-72c9-44a6-8f48-0b6a96604f49
• Source Artifact: architecture_diagram.md in the session artifacts directory
• Architectural Rationale: Closes a GUIDE_GAP identified by the DreamService for the Agent OS top-level namespace. The guide serves both human contributors and future agent instances that need to understand the system topology before performing modifications.