feat(theme-registry): pure ThemeRegistry module with full API

- 8 exports: register/unregister/list/get/categories/lightThemes/darkThemes/clear
- kebab-case id validator; category whitelist (light/dark/high-contrast/seasonal)
- duplicate-id and shape errors with descriptive messages
- pure CommonJS, no IO, no Electron deps — T2 bootstrap will register all 37 themes
- 10 Jest tests covering register/unregister/get/categories/light+dark filters
- full suite: 77 suites, 924 tests passing; lint + Prettier clean

Amit Haridas

src/main/ThemeRegistry.js

@@ -0,0 +1,108 @@
+/**
+ * Editor Theme Registry — single source of truth for installed editor themes.
+ *
+ * Pure module: no Electron, no IO, no globals beyond a module-scoped Map.
+ * The bootstrap (`ThemeRegistry.bootstrap.js`) calls `register()` at startup;
+ * `main.js` menu builder calls `list()` + `categories()`; `setTheme()`
+ * validation calls `get()`.
+ *
+ * Theme shape:
+ *   { id, label, category: 'light'|'dark'|'high-contrast'|'seasonal', isDark }
+ *
+ * Ids are kebab-case lowercase. Categories are independent of `isDark` —
+ * e.g. `winter-is-coming-light` has `isDark: false` and `category: 'light'`,
+ * but a future seasonal theme might pair `category: 'seasonal'` with
+ * `isDark: true`. Filtering by category is the public contract; `isDark`
+ * is metadata for the renderer.
+ *
+ * @module ThemeRegistry
+ */
+
+const VALID_CATEGORIES = new Set(['light', 'dark', 'high-contrast', 'seasonal']);
+const ID_RE = /^[a-z0-9]+(-[a-z0-9]+)*$/;
+
+const themes = new Map(); // id → theme
+
+function validate(theme) {
+  if (!theme || typeof theme !== 'object') throw new Error('theme must be an object');
+  if (typeof theme.id !== 'string' || !theme.id) throw new Error('theme is missing id');
+  if (!ID_RE.test(theme.id)) {
+    throw new Error(`theme id must be kebab-case lowercase: got "${theme.id}"`);
+  }
+  if (typeof theme.label !== 'string' || !theme.label) {
+    throw new Error(`theme "${theme.id}" is missing label`);
+  }
+  if (!('category' in theme) || theme.category === undefined || theme.category === null) {
+    throw new Error(`theme "${theme.id}" is missing category`);
+  }
+  if (!VALID_CATEGORIES.has(theme.category)) {
+    throw new Error(
+      `theme "${theme.id}" has invalid category "${theme.category}" (allowed: ${[...VALID_CATEGORIES].join(', ')})`
+    );
+  }
+  if (typeof theme.isDark !== 'boolean') {
+    throw new Error(`theme "${theme.id}" is missing isDark boolean`);
+  }
+}
+
+function register(theme) {
+  validate(theme);
+  if (themes.has(theme.id)) {
+    throw new Error(`duplicate theme id: ${theme.id}`);
+  }
+  themes.set(theme.id, {
+    id: theme.id,
+    label: theme.label,
+    category: theme.category,
+    isDark: theme.isDark,
+  });
+  return theme;
+}
+
+function unregister(id) {
+  return themes.delete(id);
+}
+
+function list() {
+  return [...themes.values()];
+}
+
+function get(id) {
+  return themes.get(id) || null;
+}
+
+function categories() {
+  const seen = new Set();
+  const out = [];
+  for (const t of themes.values()) {
+    if (!seen.has(t.category)) {
+      seen.add(t.category);
+      out.push(t.category);
+    }
+  }
+  return out;
+}
+
+function lightThemes() {
+  return list().filter((t) => t.category === 'light');
+}
+
+function darkThemes() {
+  return list().filter((t) => t.category === 'dark');
+}
+
+/** Test-only: empty the registry between tests. */
+function clear() {
+  themes.clear();
+}
+
+module.exports = {
+  register,
+  unregister,
+  list,
+  get,
+  categories,
+  lightThemes,
+  darkThemes,
+  clear,
+};