Resolve linked prompts in their host context

internal/framework/llm/engine_sources_test.go

@@ -161,3 +161,40 @@ func TestEngineUsesRecordedContextWithWiderRoot(t *testing.T) {
 		}
 	}
 }
+
+func TestEngineResolvesLinkedPromptMessageBesideDefinition(t *testing.T) {
+	root := t.TempDir()
+	if err := os.Mkdir(filepath.Join(root, "defs"), 0755); err != nil {
+		t.Fatal(err)
+	}
+	for name, contents := range map[string]string{
+		"config.yml":         "version: 3\n",
+		"defs/resources.yml": "prompts:\n  - id: linked\n    messages:\n      - role: user\n        content_file: message.txt\n    output:\n      format: text\n      validation_mode: none\n",
+		"defs/message.txt":   "message beside definition",
+		"message.txt":        "message beside symlink",
+	} {
+		if err := os.WriteFile(filepath.Join(root, name), []byte(contents), 0644); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := os.Symlink("defs/resources.yml", filepath.Join(root, "prompts.yml")); err != nil {
+		t.Fatal(err)
+	}
+	loaded, err := config.Load(ck.Input{Source: ck.File(filepath.Join(root, "config.yml"))}, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	runtime, err := NewRuntime(context.Background(), loaded, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	prompt, err := runtime.Engine.InspectPrompt(context.Background(), "linked")
+	if err != nil || prompt.Messages[0].Content != "message beside definition" {
+		t.Fatalf("linked prompt: %+v, %v", prompt, err)
+	}
+	for _, name := range []string{"defs/resources.yml", "defs/message.txt"} {
+		if !slices.Contains(runtime.SourcePaths, filepath.Join(root, name)) {
+			t.Errorf("missing consumed source %s in %v", name, runtime.SourcePaths)
+		}
+	}
+}