Fills in MdHeadingV1Chunker::chunk with the priority-ordered ruleset
from the design (§0 / §14):
1. Heading is a hard boundary; the heading itself starts and is
included in its chunk so heading text is retrievable.
2. Code blocks never split, regardless of size.
3. Tables stay single-chunk (row-split deferred per task spec).
4. Long sections split at target_tokens with paragraph-level
overlap_tokens worth of seeded tail blocks.
5. ImageRef / AudioRef each become their own chunk with
token_estimate = 0.
6. heading_path lifts from the first contributing non-Heading
block; source_spans concatenate in document order.
7. chunk_id derives from id_for_chunk(doc_id, chunker_version,
block_ids, policy_hash) per §4.2.
Covers the unit + determinism rows of the P1-5 test plan: heading
boundary respected, 800-token code block stays single, small table
stays single, long paragraph chain splits with overlap, ImageRef
chunk has token_estimate=0, and 1000-iter chunk_id determinism.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
altair823
0237022d0e