feat: align task pipe protocol and hmac

src/pipe/browser_tool.rs

@@ -97,6 +97,11 @@ impl<T: Transport> BrowserPipeTool<T> {
                         "received duplicate init after handshake".to_string(),
                     ));
                 }
+                BrowserMessage::SubmitTask { .. } => {
+                    return Err(PipeError::UnexpectedMessage(
+                        "received submit_task while waiting for response".to_string(),
+                    ));
+                }
             }
         }
     }

src/pipe/protocol.rs

@@ -12,6 +12,9 @@ pub enum BrowserMessage {
         #[serde(default)]
         capabilities: Vec<String>,
     },
+    SubmitTask {
+        instruction: String,
+    },
     Response {
         seq: u64,
         success: bool,
@@ -31,6 +34,14 @@ pub enum AgentMessage {
         agent_id: String,
         supported_actions: Vec<Action>,
     },
+    LogEntry {
+        level: String,
+        message: String,
+    },
+    TaskComplete {
+        success: bool,
+        summary: String,
+    },
     Command {
         seq: u64,
         action: Action,