Set default value for workspace.root and updated config documentation

internal/config/load_validate_test.go

@@ -15,6 +15,7 @@ func TestLoadAndValidate(t *testing.T) {
 		wantLoadErr  string
 		wantValidate string
 		checkDefault bool
+		wantRoot     string
 	}{
 		{
 			name: "valid minimal config",
@@ -39,6 +40,7 @@ inputs:
   glossary_file: ./glossary.yml
 `,
 			checkDefault: true,
+			wantRoot:     "/tmp/narratio",
 		},
 		{
 			name: "seriatim and audita sections can be omitted",
@@ -59,6 +61,26 @@ inputs:
   glossary_file: ./glossary.yml
 `,
 			checkDefault: true,
+			wantRoot:     "/tmp/narratio",
+		},
+		{
+			name: "workspace root defaults when omitted",
+			pipelineYAML: `whisperx:
+  transcribe_url: https://transcription.ai.rakestrawhome.com/transcribe
+analyzer:
+  timeout: 20m
+notification:
+  timeout: 15s
+`,
+			sessionYAML: `session_id: 2026-05-03
+inputs:
+  audio_dir: ./audio
+  speakers_file: ./speakers.yml
+  autocorrect_file: ./autocorrect.yml
+  glossary_file: ./glossary.yml
+`,
+			checkDefault: true,
+			wantRoot:     DefaultWorkspaceRoot,
 		},
 		{
 			name: "unknown pipeline field fails",
@@ -713,6 +735,9 @@ inputs:
 				t.Fatalf("SessionPath = %q, want %q", cfg.SessionPath, sessionPath)
 			}
 			if tt.checkDefault {
+				if tt.wantRoot != "" && cfg.Pipeline.Workspace.Root != tt.wantRoot {
+					t.Fatalf("workspace.root = %q, want %q", cfg.Pipeline.Workspace.Root, tt.wantRoot)
+				}
 				if cfg.Pipeline.WhisperX.Language != "en" {
 					t.Fatalf("whisperx.language = %q, want %q", cfg.Pipeline.WhisperX.Language, "en")
 				}