Modernize learn/benefits/Introduction.md to reflect "Application Engine" identity

The learn/benefits/Introduction.md file acts as the primary landing page for the "Getting Started" button in the Portal App. It is currently outdated, referencing "Toyota vs F1" and "Library vs Platform" in ways that predate our shift to the "Application Engine" identity.

Goal: Rewrite the introduction to align with the new strategic positioning found in the README.md and Release Notes, emphasizing Neo.mjs as an Application Engine for the AI Era.

Key Objectives:

1. Rebrand: Replace "Platform" rhetoric with "Application Engine" (Unreal Engine for the Web).
2. Deepen the Analogy: This file is the origin of the "Duplo vs. Lego Technic" analogy. It must be expanded here to explain the concept of Object Permanence (persistent runtime objects) vs. Ephemeral Render Results (melted plastic). This is the key differentiator that enables AI introspection.
3. Integrate AI Context: Introduce Context Engineering and the Neural Link as fundamental benefits of the engine architecture.
4. Structure: Create a compelling narrative that moves from the problem (UI Jank, Blind AI) to the solution (Multi-threading, Object Model).

Structure Proposal:

• Header: The Application Engine for the AI Era.
• The Mental Model: Application Engine vs. Website Builder.
• The Core Analogy: Duplo (Frameworks) vs. Lego Technic (Neo.mjs). Explain why this matters for AI (Read/Write access).
• The Architecture: Briefly touch on Multi-threading (Performance) and The Neural Link (AI).
• Conclusion: Why this matters for the future of development.