Package-level declarations

Recognizes an isolated function call.

Recognizes a multiline math block fenced by three or more dollar signs. Its closing fence is found by Line.closingFenceStart, shared with the fenced code recognizer.

Recognizes a one-line math block. The whole line must be the expression plus an optional custom ID; anything else falls through to the paragraph, where the inline math recognizer finds it instead.

Recognizes a page break. The token covers the marker alone, so its text is not line-aligned: the whitespace that must follow the marker is checked but not consumed.

Inserts the Quarkdown flavor's block recognizers into the base list: the function call right after the comment, the math blocks right after the fenced code, and the page break right after the thematic break.