Fix appearance/settings bugs: remove harmful effect cleanup, fix theme migration ordering, remove redundant reset call

- Remove useEffect cleanup that called removeThemeTokens() in useAppearance,
  which would delete the shared global <style> element when any component
  using the hook unmounted, breaking themes on navigation.

- Move t3code:theme localStorage migration before the OLD_SETTINGS_KEY guard
  in migrateLocalSettingsToServer, so users who already migrated old settings
  (or never had them) still get their theme preference migrated.

- Remove redundant updateSettings() call before resetSettings() in
  useSettingsRestore, since resetSettings already applies all defaults
  including appearance values.

Author: cursoragent

apps/web/src/components/settings/SettingsPanels.tsx

@@ -424,7 +424,7 @@ function AboutVersionSection() {
 
 export function useSettingsRestore(onRestored?: () => void) {
   const settings = useSettings();
-  const { updateSettings, resetSettings } = useUpdateSettings();
+  const { resetSettings } = useUpdateSettings();
 
   const isGitWritingModelDirty = !Equal.equals(
     settings.textGenerationModelSelection ?? null,
@@ -487,10 +487,9 @@ export function useSettingsRestore(onRestored?: () => void) {
     );
     if (!confirmed) return;
 
-    updateSettings({ colorMode: "system", activeThemeId: "t3code", accentHue: null });
     resetSettings();
     onRestored?.();
-  }, [changedSettingLabels, onRestored, resetSettings, updateSettings]);
+  }, [changedSettingLabels, onRestored, resetSettings]);
 
   return {
     changedSettingLabels,

apps/web/src/hooks/useAppearance.ts

@@ -12,7 +12,7 @@
 import { useCallback, useEffect, useMemo, useSyncExternalStore } from "react";
 import type { ColorMode } from "@t3tools/contracts/settings";
 import type { DesktopAppearance } from "@t3tools/contracts";
-import { applyThemeTokens, findThemeById, removeThemeTokens, BUILT_IN_THEMES } from "~/lib/themes";
+import { applyThemeTokens, findThemeById, BUILT_IN_THEMES } from "~/lib/themes";
 import { useSettings, useUpdateSettings } from "./useSettings";
 
 // ── Constants ────────────────────────────────────────────────────
@@ -138,8 +138,6 @@ export function useAppearance() {
 
     // Sync to Electron
     syncDesktopAppearance({ mode: colorMode, themeId: activeThemeId, accentHue });
-
-    return () => removeThemeTokens();
   }, [resolvedTheme, activeTheme, accentHue, colorMode, activeThemeId]);
 
   const setColorMode = useCallback(

apps/web/src/hooks/useSettings.ts

@@ -235,10 +235,9 @@ export function buildLegacyClientSettingsMigrationPatch(
 export function migrateLocalSettingsToServer(): void {
   if (typeof window === "undefined") return;
 
-  const raw = localStorage.getItem(OLD_SETTINGS_KEY);
-  if (!raw) return;
-
-  // Migrate old t3code:theme localStorage key to server colorMode
+  // Migrate old t3code:theme localStorage key to server colorMode.
+  // This runs independently of OLD_SETTINGS_KEY since the old useTheme hook
+  // wrote t3code:theme separately.
   try {
     const oldTheme = localStorage.getItem("t3code:theme");
     if (oldTheme === "light" || oldTheme === "dark" || oldTheme === "system") {
@@ -250,6 +249,9 @@ export function migrateLocalSettingsToServer(): void {
     // Best-effort — don't block startup
   }
 
+  const raw = localStorage.getItem(OLD_SETTINGS_KEY);
+  if (!raw) return;
+
   try {
     const old = JSON.parse(raw);
     if (!Predicate.isObject(old)) return;