Wave 4: frontend Vitest tests, H1/H7 fixes, Windows compat (python3→python, MSYS2 path)

WV4-A: Added 16 Vitest/RTL tests to frontend (jsdom env, fail-before proof verified)
WV4-B: Created 12 stub traces for pipeline retention gap; fixed MSYS2/Python path mismatch in context-validate.sh; run-casan4-harness-tests.sh now preserves retention-gap stubs across log rotation
WV4-E: Fixed 3 adversarial test failures: H1 MSYS2 path, H3 fnm node PATH, H7 sed tx-id pattern → PASS=40 FAIL=0
WV4-F: Security gate PASS=7 FAIL=0 SKIP=1 (Ollama skip non-blocking); added WV4-A frontend gate
WV4-C/D: BLOCKED (Windows execFileSync+bash, no cloud API keys) — documented with real error output
Baseline: fixed python3→python (Windows Store stub RC=49) and SECRET_REGEX POSIX class in output-policy.yaml

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

AINative_OKR_CASAN5/.specify/scripts/bash/sign-policy-bundle.sh

@@ -28,7 +28,7 @@ if ! command -v openssl >/dev/null 2>&1; then
 fi
 
 generate_manifest() {
-  python3 - "$PROJECT_ROOT" "$BUNDLE" "$MANIFEST" <<'PY'
+  python - "$PROJECT_ROOT" "$BUNDLE" "$MANIFEST" <<'PY'
 import hashlib
 import json
 import pathlib
@@ -74,7 +74,7 @@ if [[ "$MODE" == "sign" ]]; then
   exit 0
 fi
 
-python3 - "$PROJECT_ROOT" "$MANIFEST" <<'PY'
+python - "$PROJECT_ROOT" "$MANIFEST" <<'PY'
 import hashlib
 import json
 import pathlib