Recognizes a "## " heading as the start of your question — everything until the next one is the answer, however long or however it's formatted. Falls back to explicit "You:" / "Kimi:" prefixes, then plain blank lines, if no "## " is found. The split is a best-effort guess — if a turn gets split into two by mistake, use "⬆ Merge up" on the second one rather than deleting it, so no text is lost.