Fix stale daemon after upgrade causing silent CDP failures (#1134)

After upgrading agent-browser, the old daemon process keeps running.
ensure_daemon() only checks socket connectivity, not version, so the
new CLI silently reuses the old daemon — causing broken CDP behavior
with no error or warning.

Add a version sidecar file (.version) written by the daemon on startup.
ensure_daemon() now compares it against the CLI's compiled version and
automatically kills/restarts on mismatch. Missing version files (from
pre-fix or Node.js-era daemons) are treated as mismatches so the first
upgrade to this version also benefits.

Fixes #1127

Co-authored-by: ctate <366502+ctate@users.noreply.github.com>

cli/src/native/daemon.rs

@@ -62,6 +62,9 @@ pub async fn run_daemon(session: &str) {
     let pid_path = socket_dir.join(format!("{}.pid", session));
     let _ = fs::write(&pid_path, process::id().to_string());
 
+    let version_path = socket_dir.join(format!("{}.version", session));
+    let _ = fs::write(&version_path, env!("CARGO_PKG_VERSION"));
+
     // On Unix the daemon listens on a Unix domain socket; on Windows it uses
     // TCP, so there is no .sock file — only a .port file written by the server.
     let socket_path = socket_dir.join(format!("{}.sock", session));
@@ -134,6 +137,7 @@ pub async fn run_daemon(session: &str) {
         let _ = fs::remove_file(socket_dir.join(format!("{}.port", session)));
     }
     let _ = fs::remove_file(&pid_path);
+    let _ = fs::remove_file(&version_path);
     let _ = fs::remove_file(&stream_path);
     let _ = fs::remove_file(socket_dir.join(format!("{}.engine", session)));
     let _ = fs::remove_file(socket_dir.join(format!("{}.provider", session)));