markdown-stream — an incremental, streaming CommonMark/GFM parser.
Pure std, no runtime dependencies. Feed bytes to a [StreamParser] with [Parser::write] and
consume the flat [Event] stream it emits; call [Parser::flush] at end of input. The event
stream is independent of how the input is chunked (split-equivalence) — this is what makes
the parser usable on a live token stream from an LLM.
The parser is append-only and chunk-safe; renderers (markdown-html, markdown-terminal)
consume the events and never re-parse Markdown.