Major Markdown Pipeline Overhaul—Micromark-First, Proprietary Extensions, and Deep Technical Documentation

Summary of Changes

Created:
- How-Micromark-Handles-Markdown-AST.md — In-depth, step-by-step technical guide to micromark's pipeline, extension points, and tokenization model.
- How-Remark-GFM-renders-Tables.md — Exhaustive breakdown of how remark-gfm leverages micromark and mdast-util-gfm to parse/render tables, with guidance for independent reimplementation.
Purpose:
- To serve as a single source of truth for future markdown architecture, debugging, and extension development.

Created:
- Our-Extended-Markdown-Requirements-as-a-Micromark-Extension.md — Ultra-explicit, actionable prompt for building our entire extended markdown flavor as a set of micromark extensions, bypassing remark/unified entirely.
Purpose:
- To enable direct, low-level, maintainable extension development and onboarding for new contributors.

Aligned:
- All new documentation and prompts reference and enforce the requirements in Maintain-a-Proprietary-Extended-Markdown-Flavor-Rendering-Pipeline.md.
- Emphasized strict processing order, modular extension design, aggressive commenting, and error handling.

Reinforced:
- No new files outside assigned locations or naming conventions.
- All extension logic must be implemented as micromark constructs.
- TypeScript is preferred for all extension logic.

This overhaul is motivated by the need for full control, transparency, and extensibility in our markdown pipeline—removing unified/remark as a bottleneck and source of complexity.
The new documentation and prompts will drastically accelerate onboarding, debugging, and future feature development.

Begin implementation of proprietary micromark extensions per the new prompt and documentation.
Use the technical guides as the foundation for all future markdown-related work.