02354_vector_search_rescoring_distance_in_select_list fails on ARM sanitizer builds since #2341 #2546

✅ I checked the Altinity Stable Builds lifecycle table, and the Altinity Stable Build version I'm using is still supported.

Type of problem

Bug report - something's broken

Describe the situation

02354_vector_search_rescoring_distance_in_select_list has failed on every run of Stateless tests (arm_asan_ubsan, azure, parallel) since #2341 was merged on 2026-09-10. It fails on antalya-26.6 and antalya-26.8. It passes on every other job, including arm_binary.

The test returns 0.1875 where the reference expects 0.203125:

 Column: Array(Float32)
 -- Search vector: Array(Float64)
 5	0
 6	0.09375
-7	0.203125
+7	0.1875
 8	0.296875

Release builds aren't affected. They still link SimSIMD.

Root cause

#2341 stopped building SimSIMD on ARM sanitizer builds, to work around the SIGILL in #2340. Without SimSIMD, USearch converts float32 to bf16 with its own fallback (f32_to_bf16 in contrib/usearch/include/usearch/index_plugins.hpp). The fallback truncates, while SimSIMD rounds to nearest (conv.i += 0x8000). The vector index stores bf16, and the test disables rescoring, so the distance comes from the index: 2.2 becomes 2.1875 instead of 2.203125.

Possible fixes

1. Fix the SimSIMD probe and revert Antalya-26.6 - Do not build SimSIMD for ARM sanitizer builds #2341 (preferred). _simsimd_capabilities_arm is compiled under target("arch=armv8.5-a+sve"), only so the assembler accepts mrs ID_AA64ZFR0_EL1. Reading the register by its encoding (S3_0_C0_C4_4) removes the need for the SVE target. This changes the ClickHouse/SimSIMD submodule.
2. Build SimSIMD without sanitizers on ARM, with -fno-sanitize=... on the _simsimd target, then revert Antalya-26.6 - Do not build SimSIMD for ARM sanitizer builds #2341 for ASan, UBSan and TSan. This stays in our CMake, but it's untested: it assumes the SVE instruction comes from sanitizer codegen. MSan builds would still need SimSIMD disabled. Prove it with Stress test (arm_tsan).
3. Make the USearch fallback round like SimSIMD. It's a one-line change, but it lives in the ClickHouse/usearch submodule.

Current state

#2520 marks the test as broken on sanitizer builds, and only for this exact diff line. Remove that rule once one of the fixes lands.

Additional context

• Introduced by: Antalya-26.6 - Do not build SimSIMD for ARM sanitizer builds #2341 (Antalya-26.6 - Do not build SimSIMD for ARM sanitizer builds)
• Related: Stress test (arm_tsan): server dies with SIGILL in SimSIMD's ARM capability probe #2340 (SIGILL in SimSIMD's ARM capability probe)
• History (antalya-26.6, this job): 28/28 passed before Antalya-26.6 - Do not build SimSIMD for ARM sanitizer builds #2341, 8/8 failed after. Failed 3/3 reruns without random settings.
• Example run: https://github.com/Altinity/ClickHouse/actions/runs/37709892400/job/113099746696