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/governance-check.sh

@@ -50,7 +50,7 @@ hash_text() {
 }
 
 json_escape() {
-  python3 -c 'import json,sys; print(json.dumps(sys.stdin.read()))' 2>/dev/null || sed 's/\\/\\\\/g; s/"/\\"/g'
+  python -c 'import json,sys; print(json.dumps(sys.stdin.read()))' 2>/dev/null || sed 's/\\/\\\\/g; s/"/\\"/g'
 }
 
 TRACE_ID="$(new_trace_id)"
@@ -112,7 +112,7 @@ if [[ -s "$AUDIT_LOG" ]]; then
   PREV_HASH="$(tail -n 1 "$AUDIT_LOG" | sed -n 's/.*"record_hash":"\([^"]*\)".*/\1/p')"
 fi
 
-REASONS_JSON="$(printf '%s\n' "${REASONS[@]:-}" | python3 -c 'import json,sys; print(json.dumps([x for x in sys.stdin.read().splitlines() if x]))')"
+REASONS_JSON="$(printf '%s\n' "${REASONS[@]:-}" | python -c 'import json,sys; print(json.dumps([x for x in sys.stdin.read().splitlines() if x]))')"
 # approver and output_hash are part of the hashed core so they cannot be
 # silently mutated after the fact.
 RECORD_CORE="$(printf '%s|%s|%s|%s|%s|%s|%s|%s|%s|%s|%s' "$TIMESTAMP" "$TRACE_ID" "$ACTION_NAME" "$ACTOR" "$RISK_LEVEL" "$DECISION" "$APPROVAL_STATUS" "$APPROVER" "$INPUT_HASH" "$OUTPUT_HASH" "$PREV_HASH")"