deb: cleanup ephemeral context only on success

src/deb/mod.rs

@@ -48,7 +48,7 @@ pub fn build_binary_package(
     };
 
     // Create an ephemeral unshare context for all Local builds
-    let _guard = if mode == BuildMode::Local {
+    let mut guard = if mode == BuildMode::Local {
         Some(ephemeral::EphemeralContextGuard::new(series)?)
     } else {
         None
@@ -82,6 +82,11 @@ pub fn build_binary_package(
         }
     }
 
+    // Mark build as successful to trigger chroot cleanup
+    if let Some(ref mut g) = guard {
+        g.mark_build_successful();
+    }
+
     Ok(())
 }