a failed container start shows the unit's own journal lines in the op output

hive-priv-sock/src/lib.rs

@@ -255,6 +255,11 @@ pub enum PrivRequest {
     /// `nixos-container start <name>`
     StartContainer { name: String },
 
+    /// The last journal lines of `name`'s own `container@h-<name>.service`
+    /// unit since `since_unix` (seconds), returned in `stdout`. hive-priv
+    /// builds the unit name and clamps `since_unix` to the last hour.
+    StartFailureLog { name: String, since_unix: u64 },
+
     /// `nixos-container stop <name>`
     StopContainer { name: String },