Split Markdown Into Header-Aware Chunks

Implement a function that splits a Markdown document into ordered chunks, where each chunk must not exceed a given size limit.

A Markdown header is a line that starts with one to six # characters followed by a space, such as # Title or ## Section. Non-header lines belong to the current active header hierarchy.

When a new chunk starts in the middle of a section, the chunk must begin by repeating all active parent headers for the first content line in that chunk. For example, if a paragraph belongs under # Header 1 and ## Header 2, and a chunk boundary occurs immediately before that paragraph, the new chunk should start with:

# Header 1
## Header 2

followed by the paragraph.

Write a function such as:

def split_markdown(markdown: str, max_size: int) -> list[str]:
 pass

Requirements:

• Preserve the original order of the document content.
• Each returned chunk must have length at most max_size.
• Header context added to a chunk counts toward the size limit.
• Header hierarchy should be updated correctly when encountering headers of different levels.
• You may assume that any single indivisible line plus its required header context can fit within max_size.
• Define and document any reasonable assumptions about whitespace and newline handling.