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>
