Function ingest_transcript_delta 

pub fn ingest_transcript_delta(
    project_dir: &Path,
    session_id: &str,
    transcript_path: &Path,
    index_writer: Option<&dyn Fn(&str, u64, u64, &Value) -> Result<()>>,
) -> Result<IngestStats>

Perform cursor-based delta ingest from a Claude transcript JSONL file.

Reads from transcript_path starting at the cursor offset (or 0 if new), classifies records, writes kept records verbatim to the store, and returns ingest statistics.

If index_writer is Some, calls it for each kept record with (raw_line, store_offset, store_len, parsed_json) for index generation.