High-Performance Message Parser Rewrite

Rocket.Chat's current message parser uses PeggyJS, which adds bundle size overhead and performance bottlenecks. This project replaces it with a fully hand-written TypeScript recursive-descent parser that produces an identical AST, passes all existing tests, and ships with zero external dependencies. Deliverables include a complete lexer and parser implementation, 100% test suite parity, property-based fuzz testing with fast-check, and a benchmark suite demonstrating measurable performance improvements and reduced bundle size.