fix: preserve Settings Editor TOC section state across focus changes (fixes PlatformNetwork/bounty-challenge#21908)

Author: echobt

src/components/settings/SettingsEditor.tsx

@@ -34,6 +34,7 @@ import { useWorkspaceTrust } from "@/context/WorkspaceTrustContext";
 import { isSettingRestricted, getSettingRestrictionReason } from "@/utils/restrictedSettings";
 import { tokens } from "@/design-system/tokens";
 import { Button, IconButton, Input, Text, Badge, Toggle } from "@/components/ui";
+import { safeGetItem, safeSetItem } from "@/utils/safeStorage";
 import { loadStylesheet } from "@/utils/lazyStyles";
 loadStylesheet("settings");
 
@@ -105,8 +106,17 @@ interface FilterSuggestion {
   description: string;
 }
 
-// Module-level signal to persist TOC section across re-renders / focus changes
-const [persistedActiveSection, setPersistedActiveSection] = createSignal("editor");
+// Module-level signal to persist TOC section across re-renders / focus changes.
+// Back the signal with sessionStorage so the value survives lazy-chunk re-evaluation
+// and component unmount/remount cycles (e.g. switching editor tabs).
+const SETTINGS_TOC_STORAGE_KEY = "settings_active_toc_section";
+const [persistedActiveSection, _setPersistedRaw] = createSignal(
+  safeGetItem(SETTINGS_TOC_STORAGE_KEY) || "editor"
+);
+const setPersistedActiveSection = (id: string) => {
+  _setPersistedRaw(id);
+  safeSetItem(SETTINGS_TOC_STORAGE_KEY, id);
+};
 
 // =============================================================================
 // SETTINGS REGISTRY

src/components/settings/__tests__/SettingsEditor.test.tsx

@@ -19,6 +19,7 @@ vi.mock("@/context/SettingsContext", () => {
         enabled: true, fontSize: 0, fontFamily: "", showTypes: true,
         showParameterNames: true, showReturnTypes: true, maxLength: 25, padding: false,
       },
+      semanticHighlighting: { enabled: true, strings: true, comments: true },
     },
     theme: {
       theme: "dark", iconTheme: "seti", accentColor: "#007acc", uiFontFamily: "Inter",
@@ -110,6 +111,12 @@ vi.mock("@/utils/restrictedSettings", () => ({
   getSettingRestrictionReason: () => null,
 }));
 
+vi.mock("@/utils/safeStorage", () => ({
+  safeGetItem: () => null,
+  safeSetItem: () => {},
+  safeRemoveItem: () => {},
+}));
+
 vi.mock("@/utils/lazyStyles", () => ({
   loadStylesheet: () => {},
 }));