v1.40.2

fix(opencode): stop the notify plugin from crashing OpenCode at startup

After v1.40.1, OpenCode failed to start. Its log showed
"plugin config hook failed ... evaluating 'N.config'". After upgrading, run
dg configure opencode --force to replace the broken deployed plugin.

• Stop exporting exitFallbackSync from the notify.js plugin. OpenCode's
  plugin loader calls every exported function in a plugin file as a plugin and
  reads .config on what it returns. This helper returns nothing, so the read
  threw and OpenCode could not start. Its tests now go through Notify's
  existing sync-exec parameter, which also covers the real exit-listener
  wiring.
• Make the plugin loader-safety test await each export's result and fail when
  it is undefined or null. The old test only checked that each export was a
  function and did not throw, so it could not catch this crash.

Full Changelog: v1.40.1...v1.40.2