fix(native): auto_launch() honours AGENT_BROWSER_PROVIDER for cloud providers (#1126)

When a non-launch command (e.g. open, snapshot) triggers auto_launch()
before the explicit launch command is processed, auto_launch() now checks
AGENT_BROWSER_PROVIDER and connects via the provider API instead of
always falling back to a local Chrome instance.

Also redirects daemon stderr to /dev/null when not in debug mode to
prevent crashes from broken pipe after the CLI drops the piped stderr
handle. Cloud providers may write to stderr during connection setup.

Fixes #1125
Related: #979

cli/src/native/daemon.rs

@@ -41,6 +41,22 @@ pub async fn run_daemon(session: &str) {
                 session
             );
         }
+    } else {
+        // Redirect stderr to /dev/null to prevent daemon crash when the
+        // parent CLI drops the piped stderr handle after startup.  Cloud
+        // providers (AgentCore, Browserbase, etc.) may write to stderr
+        // during connection setup; a broken pipe would kill the daemon.
+        #[cfg(unix)]
+        {
+            use std::os::unix::io::IntoRawFd;
+            if let Ok(devnull) = fs::File::create("/dev/null") {
+                let fd = devnull.into_raw_fd();
+                unsafe {
+                    libc::dup2(fd, 2);
+                    libc::close(fd);
+                }
+            }
+        }
     }
 
     let pid_path = socket_dir.join(format!("{}.pid", session));