fix(migration): normalize legacy theme values under v5 marker

Two related bugs surfaced during end-to-end verification:

1. The 'isAlreadyV5' short-circuit in both the main-side and renderer-side
   v4-to-v5 transforms returned the persisted object as-is when a
   migration.version=5 marker was present. A previously-shipped v4 build
   had written theme: 'ayu-light' (and similar) under the v5 marker;
   the transform trusted the marker and passed the invalid theme through,
   which then failed the renderer's zod schema on every launch and
   reset user settings to defaults.

   Fix: in both transforms, when isAlreadyV5 matches, normalize theme
   against the v5 enum (light/dark/system) and validate the full result
   with the v5 schema before returning. Out-of-range values are replaced
   with the v5 default ('system').

2. The renderer's settings-store onRehydrateStorage callback called
   useSettingsStore.setState() to reset the store on validation failure.
   At that moment the store is still being constructed, and setState
   could hit a TDZ ReferenceError (the one we already wrapped in a
   try/catch in v5.0.0, which only hid the symptom).

   Fix: return the normalized state object from onRehydrateStorage
   instead. Zustand's persist middleware applies the returned value
   *after* construction completes, so there is no TDZ.

Tests: 334 vitest + 208 jest = 542 passing.
E2E: 12/12 verify-features.mjs steps green; no console errors.

Amit Haridas

src/main/updater/migration-transform.js

@@ -11,7 +11,36 @@ const v4SettingsSchema = z.object({
   snippets: z.array(z.unknown()).default([]),
 }).passthrough();
 
+const v5SettingsSchema = z.object({
+  fontSize: z.number().default(14),
+  tabSize: z.number().default(4),
+  lineNumbers: z.boolean().default(true),
+  wordWrap: z.boolean().default(true),
+  minimap: z.boolean().default(true),
+  theme: z.enum(['light', 'dark', 'system']).default('system'),
+  accentColor: z.string().default('brand'),
+  fontFamily: z.string().default('system'),
+  pdfFormat: z.string().default('a4'),
+  pdfMargins: z.string().default('normal'),
+  pdfEmbedFonts: z.boolean().default(true),
+  docxTemplate: z.string().default('standard'),
+  docxCustomTemplatePath: z.string().nullable().default(null),
+  replOpen: z.boolean().default(false),
+  breadcrumbSymbols: z.boolean().default(true),
+  htmlHighlightStyle: z.string().default('github'),
+  renderTablesAsAscii: z.boolean().default(false),
+  welcomeDismissed: z.boolean().default(false),
+  editorFontSize: z.number().default(14),
+  customCssPath: z.string().nullable().default(null),
+  userBindings: z.record(z.string(), z.string()).default({}),
+  updateChannel: z.enum(['github', 'concreteinfo']).default('github'),
+  autoCheckUpdates: z.boolean().default(true),
+  firstRun: z.boolean().default(true),
+  'migration.version': z.literal(5).optional(),
+}).passthrough();
+
 const v5OnlyFields = ['updateChannel', 'autoCheckUpdates', 'firstRun'];
+const v5ThemeValues = ['light', 'dark', 'system'];
 
 function isAlreadyV5(data) {
   if (!data || typeof data !== 'object') return false;
@@ -20,6 +49,18 @@ function isAlreadyV5(data) {
   return v5OnlyFields.some((f) => f in data);
 }
 
+function normalizeAlreadyV5(data) {
+  // Some earlier v5 builds wrote a legacy theme value (e.g. "ayu-light")
+  // under the v5 marker. Trusting the marker blindly broke the renderer's
+  // zod schema on every launch. Always normalize theme against the v5 enum
+  // before returning, so persisted files are always valid v5.
+  const out = { ...data };
+  if (typeof out.theme !== 'string' || !v5ThemeValues.includes(out.theme)) {
+    out.theme = 'system';
+  }
+  return out;
+}
+
 const v5SettingsShape = {
   fontSize: 14,
   tabSize: 4,
@@ -49,10 +90,12 @@ const v5SettingsShape = {
 
 function migrateV4ToV5(v4) {
   // If data already looks like v5 (has migration.version=5 or v5-only fields),
-  // return it as-is so the runner can mark it done without re-migrating.
-  // This handles the case where a buggy v5 run wrote v5 fields without the marker.
+  // normalize and validate against the v5 schema. This handles the case where
+  // a buggy v5 run wrote v5 fields without the marker, AND the case where a
+  // v5 file has a legacy theme value (e.g. "ayu-light") that would otherwise
+  // be rejected by the renderer.
   if (isAlreadyV5(v4)) {
-    return v4;
+    return v5SettingsSchema.parse(normalizeAlreadyV5(v4));
   }
   const parsed = v4SettingsSchema.parse(v4 || {});
   return {
@@ -67,4 +110,4 @@ function migrateV4ToV5(v4) {
   };
 }
 
-module.exports = { migrateV4ToV5, v5SettingsShape };
+module.exports = { migrateV4ToV5, v5SettingsShape };