Migrate test plugins to Rust and async-ify syscall modules

- Replace Python test plugins (echo, ai_test, claudecode) with Rust
  implementations driven by the plugin SDK
- Convert fs/network/process/timer syscall modules to async/await
- Change Network.OpenConn to return stream ConnEvent (conn_id handed
  to client in first "open" frame for Send/Close routing)
- Bind timer callbacks to plugin identity; stream_call subscriptions
  are identity-checked
- Update docs and regenerate Python SDK protobuf stubs

Verified: cargo build/test/clippy clean; echo + ai_test full syscall
suites pass; hermes & claudecode register and heartbeat; cross-plugin
bridge.call routing and auth denial verified end-to-end.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/04-项目结构.md

@@ -51,22 +51,21 @@ Agentsd/
     │   ├── agentsd_pb2.py
     │   └── agentsd_pb2_grpc.py
     │
-    ├── echo/                      # 测试插件
+    ├── echo/                      # 测试插件(Rust)
     │   ├── plugin.yaml
-    │   └── echo_plugin.py
+    │   └── src/main.rs
     │
-    ├── ai_test/                   # AI 手动验证插件(enabled=false,autoload=false)
+    ├── ai_test/                   # AI 手动验证插件(Rust,enabled=false,autoload=false)
     │   ├── plugin.yaml
-    │   └── ai_test_plugin.py
+    │   └── src/main.rs
     │
-    ├── hermes/                    # Hermes Agent 桥接(63 tool)
+    ├── hermes/                    # Hermes Agent 桥接(Python,Rust 版仅 stub)
     │   ├── plugin.yaml
     │   └── hermes_plugin.py
     │
-    └── claudecode/                # Claude Code CLI 桥接
+    └── claudecode/                # Claude Code CLI 桥接(Rust)
         ├── plugin.yaml
-        ├── claudecode_plugin.py
-        └── test_chat.py
+        └── src/main.rs
 ```
 
 ## 布局原则
@@ -94,7 +93,7 @@ cargo build --release       # 约 6.1MB 单二进制
 
 # 启动插件(各开一个终端)
 python plugins/hermes/hermes_plugin.py
-python plugins/claudecode/claudecode_plugin.py
+cargo run -p agentsd-plugin-claudecode
 ```
 
 ## 手动验证插件
@@ -103,7 +102,7 @@ python plugins/claudecode/claudecode_plugin.py
 
 ```bash
 RUST_LOG=agentsd=info ./target/release/agentsd.exe
-python plugins/ai_test/ai_test_plugin.py
+cargo run -p agentsd-plugin-ai-test
 ```
 
 ## 重新生成 SDK