fix(coding): add missing height-parity guard to AVX2 fused-dequant

The NEON and WASM variants gate fused dequant on both
(size.x & 3)==0 and (size.y & 1)==0, but the AVX2 path only
checked width.  With odd-height blocks the last quad-pair's
second-row store overflows into the adjacent block's i_samples
region, causing a data race under multi-threaded decode_strip_core
dispatch (flaky comp_p1_ht_05_11 on CI).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: osamu620

source/core/coding/ht_block_decoding_avx2.cpp

@@ -1130,7 +1130,8 @@ bool htj2k_decode(j2k_codeblock *block, const uint8_t ROIshift) {
     // adjacent blocks' column range in the shared output buffer (subband or ring buffer).
     // This is safe in single-threaded decode (sequential order overwrites correctly) but
     // causes a data race in multi-threaded decode.  Gate on width % 4 == 0 to avoid this.
-    if (num_ht_passes == 1 && ROIshift == 0 && (block->size.x & 3) == 0) {
+    if (num_ht_passes == 1 && ROIshift == 0 && (block->size.x & 3) == 0
+        && (block->size.y & 1u) == 0) {
       ht_cleanup_decode<true, true>(block, static_cast<uint8_t>(30 - S_blk), Lcup, Pcup, Scup);
       dequant_done = true;
     } else if (num_ht_passes == 1) {