feat: add browser script skill execution

tests/pipe_protocol_test.rs

@@ -1,4 +1,6 @@
-use sgclaw::pipe::{Action, AgentMessage, BrowserMessage, SecurityFields, Timing};
+use sgclaw::pipe::{
+    Action, AgentMessage, BrowserMessage, ExecutionSurfaceKind, SecurityFields, Timing,
+};
 
 #[test]
 fn browser_init_round_trip_uses_frozen_wire_format() {
@@ -57,3 +59,32 @@ fn response_deserializes_timing_and_payload() {
         }
     );
 }
+
+#[test]
+fn submit_task_exposes_browser_context_without_implying_browser_only_runtime() {
+    let message = BrowserMessage::SubmitTask {
+        instruction: "统计一下知乎热榜".to_string(),
+        conversation_id: "conversation-1".to_string(),
+        messages: vec![],
+        page_url: "https://www.zhihu.com/hot".to_string(),
+        page_title: "知乎热榜".to_string(),
+    };
+
+    let context = message.browser_context().expect("browser context");
+    let surface = message
+        .requested_surface_metadata()
+        .expect("surface metadata");
+
+    assert_eq!(context.page_url, "https://www.zhihu.com/hot");
+    assert_eq!(context.page_title, "知乎热榜");
+    assert_eq!(surface.kind, ExecutionSurfaceKind::PrivilegedBrowserPipe);
+    assert!(surface.privileged);
+    assert!(!surface.defines_runtime_identity);
+}
+
+#[test]
+fn supported_actions_include_browser_script_execution() {
+    let supported = sgclaw::pipe::supported_actions();
+
+    assert!(supported.iter().any(|action| action.as_str() == "eval"));
+}