P0 fixes from test report review:
- object unit_id: fallback to f"{obj_type}:p{page}:{block_id}" when
figure_id/table_id missing (prevents DB overwrite on INSERT OR REPLACE)
- object caption_key: page-qualified f"p{page}:{caption_bid}" to match
page-qualified subtree_block_ids in find_owning_node
- object block_map: page-qualified keys for consistency with body_units
- structure node_id: changed from sec:{block_id} to sec:p{page}:{block_id}
for stability (reduces vector ID churn from emitted_order changes)
New tests:
- Section 4b: Object units DB persistence (unit_id unique, non-empty labels,
DB count == list count after upsert)
- Section 5b: Coverage gate (v2_tree / render_map / body_papers counts)
Layer A: 1669/1669 pass (+60 checks from 4b + 5b)
Unit tests: 153 pass, 1 skip
- _body_unit_role_kind now excludes only reference_item/reference_heading
(per policy: everything in fulltext except ref zone)
- backmatter_body unit_kind removed; all units are 'body'
- bounds_map in structure_tree uses page-qualified key (fixes collision
when same block_id appears on different pages)
- Layer A test plan: emitted_ids uses page-qualified keys + handles
block_id=0 (falsy value)
- Layer A: 1609 passed, 0 failed on real vault (22 papers)
- Unit tests: 152 passed, 1 pre-existing skip
- Section/subsection headings now appear in BOTH heading_events and
emitted_block_events (emitted_as='heading') for complete event stream
- Backmatter headings (Funding/Acknowledgments/Data Availability/Conflicts)
now generate heading_events → appear as structure tree sections with
their own body_units
- Page-qualified block IDs (p{page}:{block_id}) in tree own/subtree_block_ids
and body_units block_map: eliminates ambiguous block_id collisions when
same block_id appears on multiple pages in real OCR data
- TC-9.2 wording fix, KEYS empty guard, global unit_id uniqueness check
- _split_if_oversized: recursive _halve_text until every part <= 1000 tokens
- _incremental_units_only: also checks retrieval_policy_version match
- _rebuild_paper_units: use RETRIEVAL_POLICY_VERSION constant
- Functional test plan: Layer A (artifact) + Layer B (API), all 8 review
fixes incorporated (persisted artifacts, no jump-assertion, stronger
object/backmatter/abstract tests, proper embed flow)
- RenderOutput dataclass with heading_events/emitted_block_events tracking
- Stack-algorithm structure tree with own/subtree block IDs
- Recursive body_units builder with role helper + token cap splitting
- Schema v4: section_path_json, section_level, section_title, part_ordinal
- Phase 4/5 reorder in ocr_rebuild.py and ocr.py
- 12 new test cases for tree nesting, own_block_ids, rendered-order intervals
