test(landscape): make node-failure test deterministic under sibling cancellation

Scope the stub publisher failure to node 00's output; when every stage-0
publish failed, the first failing sibling cancelled node 00 and its
recorded error was "context canceled" instead of the publish error.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

internal/service/landscape_test.go

@@ -332,11 +332,15 @@ type stubPublisher struct {
 	created  []CreateRasterInput
 	uploaded []UploadInput
 	err      error
+	// errFilename, when set, scopes err to publishes of that output file only,
+	// so a test can fail exactly one node while its stage siblings succeed
+	// (a sibling failing first would cancel the node under test).
+	errFilename string
 }
 
 func (p *stubPublisher) CreateRasterFromFile(ctx context.Context, in CreateRasterInput) (domain.Dataset, error) {
 	p.mu.Lock()
-	if p.err != nil {
+	if p.err != nil && (p.errFilename == "" || p.errFilename == in.Filename) {
 		p.mu.Unlock()
 		return domain.Dataset{}, p.err
 	}
@@ -1235,7 +1239,13 @@ func TestLandscapeService_Execute_NodeFailureFailsRunAndCleansUp(t *testing.T) {
 		},
 		{
 			name: "publishing the result fails",
-			arrange: func(f *lpFixture) { f.pub.err = errors.New("minio down") },
+			arrange: func(f *lpFixture) {
+				// Fail only node 00's output: if every stage-0 publish failed,
+				// whichever sibling failed first would cancel node 00 and its
+				// recorded error would be "context canceled" instead.
+				f.pub.err = errors.New("minio down")
+				f.pub.errFilename = landscape.OutZIntegrated + ".tif"
+			},
 			want: "minio down",
 		},
 	}