Feat: Implement Neo.component.markdown.VDom (VDOM-Native Parsing)

[tobiu]

Create a new Markdown component that compiles markdown source directly into a Neo.mjs VDOM tree, bypassing innerHTML and the marked library.

Architecture:

• Input: Markdown string (or stream).
• Output: Pure VDOM Tree (e.g., {tag: 'p', cn: [{vtype: 'text', html: 'Hello'}]}).
• Parser: A lightweight, custom parser running in the App Worker.

Benefits:

1. Delta Updates: Enables fine-grained DOM patching for streaming content (LLM responses).
2. Security: Eliminates XSS risks associated with innerHTML.
3. Performance: Avoids full DOM trashing on every character append.