feat: 重构项目结构并添加核心功能

refactor: 将代码按功能模块重新组织到 core/runtime/control 等目录
feat(core): 添加 Context、FlowNode 等核心 trait 和类型
feat(runtime): 实现 FlowEngine 和状态管理
feat(control): 添加顺序/并行/条件控制流节点
feat(nodes): 实现 HTTP/DB/MQ 等业务节点
docs: 更新 README 添加架构说明和快速开始示例
test: 添加性能测试脚本和示例代码

scripts/test_report.sh

@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+
+set +e
+
+JS_FEATURE=0
+if [[ "$1" == "--js" ]]; then
+  JS_FEATURE=1
+fi
+
+dir="target/test-reports"
+docDir="doc"
+mkdir -p "$dir"
+mkdir -p "$docDir"
+
+if [[ "$JS_FEATURE" == "1" ]]; then
+  header="## JS feature"
+  outFile="$docDir/performance-js.md"
+  featureArgs="--features js"
+else
+  header="## Default features"
+  outFile="$docDir/performance-default.md"
+  featureArgs=""
+fi
+
+names=(test_rhai_expr_set_and_get test_conditional_node_then_else test_http_node_with_mock test_stateful_engine test_db_and_mq_nodes test_group_parallel_sleep test_expr_set_without_engine_error)
+if [[ "$JS_FEATURE" == "1" ]]; then
+  names+=(test_js_expr_and_fork_join)
+fi
+
+md="# dsl-flow Test Performance\n\n${header}\n"
+for n in "${names[@]}"; do
+  # Measure elapsed seconds with bash time builtin
+  TIMEFORMAT='%3R'
+  dur=$( { time cargo test -p dsl-flow ${featureArgs} -- --exact "${n}" --nocapture --quiet >/dev/null; } 2>&1 )
+  md+="- ${n}: ${dur}s\n"
+done
+
+printf "%b" "$md" > "$outFile"
+echo "Report written to $outFile"
+