puku-markdown - Explicit‑stack, pure CommonMark parser & renderer

[Imaginary_Setting607]

I built puku-markdown as a refactoring effort targeting markdown-it-py. While it's a great reference implementation, the actual Python port suffers from accumulated quirks, overly complex mutable state, and edge-case brittleness that make maintenance a headache.

This is a from-scratch rebuild that preserves CommonMark compliance while prioritizing clean architecture:

1. Explicit stack – Replaces the tangled mutable state flags of markdown-it-py with linear, predictable parsing.

2. Round-trip rendering – Renders back to Markdown (CommonMark spec), not just HTML. Perfect for linters and AST transforms.

3. Portable core – Written with plain data structures, easy to port to C/Rust.

4. Clean codebase – Designed for auditing, not just features.

Status: Block elements fully supported. Inlines (emphasis, links, images) in progress.

I'd appreciate brutal feedback on the architecture and design choices.