feat: 完成错误原因合同与付款就绪提示（09-05-error-explainability-payment-readiness）

scripts/qa/run-release-gate.sh

@@ -89,6 +89,8 @@ stage_project_wide_static() {
   local issue_csv="$ROOT_DIR/issues/2026-05-08_23-38-37-project-wide-qa-second-pass.csv"
   python3 /home/shunli/.codex/skills/plan/scripts/validate_issues_csv.py "$issue_csv"
   node "$ROOT_DIR/scripts/qa/check-ui-design-rules.mjs" --strict
+  node "$ROOT_DIR/scripts/qa/check-error-reason-contract.mjs" --strict
+  node "$ROOT_DIR/scripts/qa/check-error-reason-contract.mjs" --self-test
   node "$ROOT_DIR/scripts/qa/check-mobile-route-contract.mjs"
   node "$ROOT_DIR/scripts/qa/check-flow-coverage.mjs" --json > "$ARTIFACT_ROOT/flow-coverage.json"
   node "$ROOT_DIR/scripts/qa/check-flow-coverage.mjs" --markdown "$ARTIFACT_ROOT/flow-coverage.md"