Add workspace configuration support

internal/core/config/file_config_test.go

@@ -554,6 +554,95 @@ diagnostics:
 	}
 }
 
+func TestApplyFileConfigWorkspaceSection(t *testing.T) {
+	cfg := parseAndApplyConfig(t, `
+version: 2
+workspace:
+  directory: /var/lib/notarius
+  diagnostics:
+    enabled: false
+    retention: never
+  resume:
+    enabled: true
+  debug:
+    enabled: true
+diagnostics:
+  work_dir: /tmp/legacy
+  retention: always
+`)
+
+	if cfg.Workspace.Directory != "/var/lib/notarius" {
+		t.Fatalf("workspace directory = %q, want /var/lib/notarius", cfg.Workspace.Directory)
+	}
+	if cfg.DiagnosticsEnabled() {
+		t.Fatalf("expected diagnostics disabled")
+	}
+	if cfg.Diagnostics.WorkDir != "/var/lib/notarius/diagnostics" {
+		t.Fatalf("effective diagnostics work dir = %q, want workspace diagnostics root", cfg.Diagnostics.WorkDir)
+	}
+	if cfg.Diagnostics.Retention != diagnostics.RetentionNever {
+		t.Fatalf("effective diagnostics retention = %q, want workspace override", cfg.Diagnostics.Retention)
+	}
+	if !cfg.Workspace.Resume.Enabled {
+		t.Fatalf("expected resume enabled")
+	}
+	if !cfg.Workspace.Debug.Enabled {
+		t.Fatalf("expected debug enabled")
+	}
+}
+
+func TestApplyFileConfigLegacyDiagnosticsRemainCompatible(t *testing.T) {
+	cfg := parseAndApplyConfig(t, `
+version: 2
+diagnostics:
+  work_dir: /tmp/legacy
+  retention: always
+`)
+
+	if cfg.Workspace.Directory != "" {
+		t.Fatalf("workspace directory = %q, want unset", cfg.Workspace.Directory)
+	}
+	if !cfg.DiagnosticsEnabled() {
+		t.Fatalf("expected diagnostics enabled")
+	}
+	if cfg.Diagnostics.WorkDir != "/tmp/legacy" {
+		t.Fatalf("effective diagnostics work dir = %q, want legacy", cfg.Diagnostics.WorkDir)
+	}
+	if cfg.Diagnostics.Retention != diagnostics.RetentionAlways {
+		t.Fatalf("effective diagnostics retention = %q, want legacy", cfg.Diagnostics.Retention)
+	}
+}
+
+func TestApplyFileConfigWorkspaceRetentionOverridesLegacyRetentionOnlyWhenSet(t *testing.T) {
+	t.Run("legacy retained", func(t *testing.T) {
+		cfg := parseAndApplyConfig(t, `
+version: 2
+workspace:
+  directory: /var/lib/notarius
+diagnostics:
+  retention: never
+`)
+		if cfg.Diagnostics.Retention != diagnostics.RetentionNever {
+			t.Fatalf("effective diagnostics retention = %q, want legacy", cfg.Diagnostics.Retention)
+		}
+	})
+
+	t.Run("workspace overrides", func(t *testing.T) {
+		cfg := parseAndApplyConfig(t, `
+version: 2
+workspace:
+  directory: /var/lib/notarius
+  diagnostics:
+    retention: always
+diagnostics:
+  retention: never
+`)
+		if cfg.Diagnostics.Retention != diagnostics.RetentionAlways {
+			t.Fatalf("effective diagnostics retention = %q, want workspace", cfg.Diagnostics.Retention)
+		}
+	})
+}
+
 func parseAndApplyConfig(t *testing.T, raw string) Config {
 	t.Helper()
 	fileCfg, err := ParseFileConfigYAML([]byte(raw))