Fix Windows MSVC build: hoist CB*_I8_RECIP out of __ARM_NEON guard

[unamedkr]

Summary

Fixes the 8 consecutive Windows CI failures since Round 10 (commit 24136353619). All recent CI runs on main are red on windows-latest (x64) with:

src\core\tq_turbo_kv.c(365,33): error C2065: 'CB3_I8_RECIP': undeclared identifier
src\core\tq_turbo_kv.c(585,33): error C2065: 'CB_I8_RECIP': undeclared identifier
src\core\tq_turbo_kv.c(1324,33): error C2065: 'CB5_I8_RECIP': undeclared identifier

Root cause

Round 10/11 added three int8 codebook reciprocal constants inside #ifdef __ARM_NEON blocks:

#ifdef __ARM_NEON
    static int8_t s_cb3_i8[16] = {0};
    static int s_cb3_i8_init = 0;
    static const float CB3_I8_RECIP = 2.1520f / 127.0f;   // ← trapped inside guard
    ...
#endif

    for (int seq = 0; seq < seq_len; seq++) {
        ...
        float per_block_scale = CB3_I8_RECIP / inv_std;   // ← used outside guard

NEON builds happened to compile because the guard contains the declaration in the same translation unit. MSVC x64 (no __ARM_NEON) sees the use without the declaration and errors out.

Fix

Hoist all three static const float CB*_I8_RECIP declarations one line above their #ifdef __ARM_NEON openings. They're plain floats, not NEON-typed. Six insertions, three deletions, no behavior change.

Test plan

• macOS arm64 NEON build (cmake --build build) — passes
• Windows MSVC x64 CI — needs this PR's run
• Linux x86_64 CI

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