config: add ServiceConfig.WorkerRootPath() to guard documented layout

The <workspaces_root>/.workers derivation moved from a config.Parse default
into example/main.go when ServiceConfig.WorkerRootPath was removed, but it
was untested there (package main). Move it into config as a small method
with its own test, so the layout documented on WorkspacesRoot can't drift
silently again.

Author: yushan8

config/config_test.go

@@ -70,6 +70,13 @@ repository:
 	}
 }
 
+func TestServiceConfig_WorkerRootPath(t *testing.T) {
+	// Guards the layout documented on ServiceConfig.WorkspacesRoot:
+	// <workspaces_root>/.workers for worker checkouts.
+	svc := ServiceConfig{WorkspacesRoot: "/tmp/x"}
+	assert.Equal(t, filepath.Join("/tmp/x", ".workers"), svc.WorkerRootPath())
+}
+
 func TestParse_ServiceDefaults(t *testing.T) {
 	tests := []struct {
 		name                      string

config/service_config.go

@@ -14,6 +14,8 @@
 
 package config
 
+import "path/filepath"
+
 // ServiceConfig holds operational configuration for the Tango service.
 type ServiceConfig struct {
 	// MaxWorkerPoolSize is the max number of concurrent requests per repository.
@@ -28,6 +30,12 @@ type ServiceConfig struct {
 	Streaming      ChunkConfig `yaml:"streaming"` // streaming chunk sizes; zero values fall back to package defaults
 }
 
+// WorkerRootPath returns the root directory for worker workspace checkouts,
+// as documented on WorkspacesRoot: <workspaces_root>/.workers.
+func (s ServiceConfig) WorkerRootPath() string {
+	return filepath.Join(s.WorkspacesRoot, ".workers")
+}
+
 // ChunkConfig controls the number of entries per gRPC stream message.
 // All fields are optional; a zero value means "use the package default".
 // Tune these when a monorepo's per-target size causes messages to approach

example/main.go

@@ -72,7 +72,7 @@ func run() error {
 
 	// Repo manager and orchestrator
 	repoManagerClonePath := cfg.Service.WorkspacesRoot
-	workerRootPath := filepath.Join(repoManagerClonePath, ".workers")
+	workerRootPath := cfg.Service.WorkerRootPath()
 	if err := os.MkdirAll(repoManagerClonePath, 0o755); err != nil {
 		return fmt.Errorf("failed to create repo manager clone path: %w", err)
 	}