v0.3.5

Fix a batch-dependent neighbor-selection issue with donor_policy="available": a numerically suspect query could change another query's imputed value when the two were transformed together.

• Apply direct float64 distance refinement per affected query.
• Refine relevant float32 distance ties, including ties crossing the candidate boundary, and resolve equal refined distances in training-row order.
• Add regressions for mixed batches, candidate expansion, tie handling, and cache cleanup.

Validation: 150 tests passed for the fix. A same-runner main/clean/clean/main benchmark covered 24 Available configurations, with mean transform-time changes ranging from -3.92% to +0.72%. No material slowdown was observed in that workload; two observations per version do not establish a speedup or precise overhead, and tie-heavy workloads were not separately benchmarked.

The existing heuristic numerical-risk detection remains unchanged; this fix does not guarantee exact neighbor ordering for every floating-point input.