Function parse_prompt_tool_carrier 

pub fn parse_prompt_tool_carrier(content: &str) -> Option<CarrierParts>

Parse a prompt-mode carrier: line 1 the results prefix, line 2 the exact count header, then exactly that many marker lines, then the body.

Returns None when line 1 is not the results prefix (not a carrier). A carrier whose line 2 is not a count header is legacy: zero attachments and the full text — prefix included — as the body. A count header whose marker lines are missing or malformed is corrupt and falls back to the same legacy reading, so a damaged carrier degrades to text rather than to a wrong attachment list.