feat: 引入 Rust executor/gateway sidecar 及 Python 侧双后端适配

- 新增 Rust workspace crates: aether-contracts, aether-executor, aether-gateway
- aether-executor: 支持 Unix Socket/TCP 双传输模式，处理同步/流式上游请求
- aether-gateway: 作为本地主入口代理，集成 /api/internal/gateway/resolve 认证预解析
- Python 侧新增 ExecutionPlan 契约和 RustExecutorClient，各 handler 支持
  executor_backend=rust 时将可序列化请求转发给 Rust executor 执行
- 重构 dev.sh 支持 executor/gateway 进程编排与生命周期管理
- 新增 internal gateway 路由，提供 resolve/passthrough 端点
- handler 层(chat/cli/video/endpoint_checker 等)全面适配 Rust executor 回退逻辑
- pipeline 层支持 trusted auth context 跳过重复认证
- 新增 Rust CI workflow 及对应测试用例

crates/aether-contracts/src/result.rs

@@ -0,0 +1,40 @@
+use std::collections::BTreeMap;
+
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
+
+use crate::ExecutionError;
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+pub struct ExecutionTelemetry {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub ttfb_ms: Option<u64>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub elapsed_ms: Option<u64>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub upstream_bytes: Option<u64>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+pub struct ResponseBody {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub json_body: Option<Value>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub body_bytes_b64: Option<String>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+pub struct ExecutionResult {
+    pub request_id: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub candidate_id: Option<String>,
+    pub status_code: u16,
+    #[serde(default)]
+    pub headers: BTreeMap<String, String>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub body: Option<ResponseBody>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub telemetry: Option<ExecutionTelemetry>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub error: Option<ExecutionError>,
+}