feat: add websocket browser service runtime

Wire the service/browser runtime onto the websocket-driven execution path and add the new browser/service modules needed for the submit flow and runtime integration.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/pipe/protocol.rs

@@ -55,6 +55,9 @@ pub enum BrowserMessage {
         #[serde(default)]
         capabilities: Vec<String>,
     },
+    Connect,
+    Start,
+    Stop,
     SubmitTask {
         instruction: String,
         #[serde(default)]
@@ -119,6 +122,9 @@ pub enum AgentMessage {
         agent_id: String,
         supported_actions: Vec<Action>,
     },
+    StatusChanged {
+        state: String,
+    },
     LogEntry {
         level: String,
         message: String,