[mikessh]

Behavior

Add native Index.search_batch_consume and Index.search_paired_batch_consume APIs for complete-query hit buffers with explicit byte limits. Callbacks remain serial, own their buffers and propagate failures after worker cleanup. Coordinated searches share one native pool; skip_empty=True preserves the other axis and original offsets when a query partner is absent.

These are the existing downstream prerequisites for antigenomics/vdjmatch#41. Released seqtree 1.2.0 does not contain them. No Python search fallback or downstream score change is introduced.

Verification

• Full Python suite against the exact candidate extension: 1,039 passed, 2 skipped in 9.22 s.
• Focused single/paired consumer suite: 21 passed in 1.16 s.
• Current C++ tree rebuilt with four compiler workers; ctest passes (0.56 s).
• Tests cover legacy-hit equality, duplicate identities, empty axes, callback errors, explicit overflow, parameter snapshots, serial callbacks and bounded dense-hit memory.

Release packaging/platform CI and an owner-approved release remain prerequisites for vdjmatch's released-dependency CI. The author approved the dependency release after green CI; metadata is now 1.3.0. Publication follows integration and the existing release workflow, not this PR creation.