## Description
`HNSWVectorIndex.index_batch()` used the live memory map size to decide
whether to resize hnswlib before adding new labels. hnswlib does not
reclaim capacity slots when labels are removed with `mark_deleted`, so
after delete/evict churn the live count can be much lower than the
assigned-id high-water mark. That lets a batch add skip resizing and
then fail in `add_items` with `number of elements exceeds the specified
limit`.
## Fix
- Size the batch resize check from `self._next_hnsw_id`, which has
already been incremented for the new batch labels.
- Match the single-item `index()` path's high-water-mark capacity
behavior.
- Add a regression test that deletes most entries from a small index and
then batch-adds enough new memories to require a resize.
- Merge current `main` to refresh mergeability and stale lint results.
## Testing
```text
uvx ruff@0.15.17 check headroom/memory/adapters/hnsw.py tests/test_memory/test_hnsw_batch_capacity.py headroom/memory/factory.py
All checks passed!
uvx ruff@0.15.17 format --check headroom/memory/adapters/hnsw.py tests/test_memory/test_hnsw_batch_capacity.py headroom/memory/factory.py
3 files already formatted
git diff --check headroomlabs/main...HEAD
# no output
uv run --extra dev python -m pytest tests/test_memory/test_hnsw_batch_capacity.py -q
1 passed, 18 warnings
```
## Review Readiness
- [x] Ready for review
- [x] Regression test added
- [x] CHANGELOG updated
Co-authored-by: JerrettDavis <mxjerrett@gmail.com>
Co-authored-by: Tejas Chopra <chopratejas@gmail.com>
