release: restore ZUPT and harden source-only 5.2.2

tests/test_ct_timing.sh

@@ -2,7 +2,7 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
 # Copyright (c) 2025-2026 Cristian Cezar Moisés
 #
-# dudect-style constant-time verification of zupt_ct_memeq (v3.5.0).
+# dudect-style timing regression measurement for zupt_ct_memeq (v3.5.0).
 # Builds at -O2 (the shipped optimisation level — so this tests the code
 # as users run it, including that the volatile accumulator survives the
 # optimiser) and runs the Welch t-test harness.
@@ -15,7 +15,6 @@
 # passing vacuously.
 
 set -u
-SDK_DIR="${ZUPTSDK_DIR:-vendor/zuptsdk}"
 ARCH=$(uname -m)
 if [ "$ARCH" = "x86_64" ] || [ "$ARCH" = "i686" ]; then
     SHANI="-msha -mssse3 -msse4.1"
@@ -24,19 +23,14 @@ else
 fi
 
 TMP=$(mktemp -d)
-# This test uses only native CT primitives (zupt_ct_memeq, ML-KEM CT compare);
-# the libzuptsdk linkage is vestigial. Link it only when the vendored library
-# is present (WITH_SDK builds); source-only builds compile+run without it.
-SDK_LINK=""
-if ls "$SDK_DIR"/libzuptsdk.so* >/dev/null 2>&1; then
-    SDK_LINK="-L$SDK_DIR -lzuptsdk -Wl,-rpath,$(cd "$SDK_DIR" && pwd)"
-fi
-if gcc -Iinclude -Isrc -I"$SDK_DIR/include" -Wall -Wextra -Werror $SHANI -O2 -std=c11 \
+# This test uses only native CT primitives; it deliberately has no optional
+# SDK linkage so the baseline source build is the exact path under test.
+if "${CC:-cc}" -Iinclude -Isrc -Wall -Wextra -Werror $SHANI -O2 -std=c11 \
        tests/test_ct_timing.c \
        src/zupt_crypto.c src/zupt_sha256.c src/zupt_sha256_shani.c src/zupt_aes256.c \
        src/zupt_xxh.c src/zupt_keccak.c src/zupt_x25519.c src/zupt_mlkem.c \
        src/zupt_cpuid.c src/zupt_mlock.c \
-       $SDK_LINK -lm \
+       -lm \
        -o "$TMP/t" 2>"$TMP/cc.log"; then
     "$TMP/t"; rc=$?
 else
@@ -48,8 +42,8 @@ rm -rf "$TMP"
 
 # Source-routing guard: the security-critical compares must use the single
 # audited zupt_ct_memeq primitive, not a reintroduced inline byte-OR loop.
-# This is what makes the 32-byte timing proof transfer to the ML-KEM
-# 1088-byte decaps compare (same function, length-independent).
+# This confirms that the measured primitive is also used by the ML-KEM
+# 1088-byte decapsulation comparison; it is not a formal timing proof.
 echo ""
 echo "  -- source routing (audited primitive) --"
 ROUTE_OK=0