Add notifications about disk space

Two trigger points: disk space low and disk space exhausted.

Ideally this is a native system notification, not just a notification that appears in the Gateway window since the window could be minimized or obscured.

Start by locating the plugin entry points that monitor workspace disk space and the Gateway window notification path. Trace both low-space and exhausted-space conditions, then determine how native system notifications are exposed by the JetBrains plugin. Done means both conditions notify users even when the Gateway window is minimized or obscured.

Vom Indexierungsmodell aus dem Issue-Text verfasst.