feat: enable one2many batch distance for ip and l2

[kgeg401]

Summary

• enable one-to-many batch distance path for:
  • InnerProduct metric
  • SquaredEuclidean (L2) metric
• switch dense/int8/int4 batch-distance wiring from 1,1 to 12,2
• add regression tests that compare scalar distance vs batch distance for FP32 and INT8

Why

Issue #97 requests enabling one2many for IP and L2. Existing wiring in these metrics used single-lane batch settings, while cosine already uses one2many-capable settings.

Validation

• added unit tests in:

  • ests/core/metric/inner_product_metric_test.cc
    

  • ests/core/metric/euclidean_metric_test.cc
    

• note: local environment lacks a usable C/C++ compiler toolchain, so test execution is deferred to CI

Fixes #97

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