feat(i18n): localize plugin catalog names and shell preset desc

Catalog entry names (15 tab + 4 viewer) and the dsh-desktop shell preset
desc were raw hardcoded zh strings rendered straight into the add-plugin
modals and the title-bar scheme dropdown. Mirror the existing desc
pattern exactly: PluginEntry.name / ShellPreset.desc widen to the
i18n-friendly string-or-() =>-string union, the catalogs carry lazy
t('pluginXxxName') / t('presetDshDesktopDesc') lookups, and the
add-plugin modal (render, search filter, aria-labels) plus the scheme
SelectMenu resolve them like every other copy. The plain-string arm of
the union stays as the raw-name fallback, and t() itself never yields
empty text (missing keys render the key), so a dict gap can never blank
a name.

20 new dictionary keys added to zh/en (locales.ts), ja (locales-ja.ts),
and all 18 third-language dictionaries — tests/locales.spec.ts enforces
key-set equality against zh for every shipped dict (precedent: 9cc642b),
so the 'leave other locales-* untouched' shortcut would fail the hard
parity gate; real translations are provided instead.

Spec follow-ups (behavior change: names/descs now render through t()):
- plugin-list.spec.ts: name non-empty assertion resolves the union.
- add-plugin-modal.spec.tsx: sentinel/office name assertions resolve
  from the catalog (en locale in tests) instead of pinning zh literals.
- shell-presets.spec.ts: desc non-empty assertion resolves the union.

tests/shell-presets.spec.ts

@@ -1,13 +1,21 @@
 /**
  * Built-in shell-preset data tests: registry integrity (unique ids, non-empty
- * titles, pure strip/detect functions) and the anywhere-labs DSH Desktop
- * entry's strip values (darwin advanced 20px, win32 advanced 32px as the
- * no-WCO fallback, compatibility/plain browser nothing).
+ * titles, non-empty localized descs, pure strip/detect functions) and the
+ * anywhere-labs DSH Desktop entry's strip values (darwin advanced 20px,
+ * win32 advanced 32px as the no-WCO fallback, compatibility/plain browser
+ * nothing).
  */
 import { describe, expect, it } from 'vitest'
 import { getShellPreset, getShellPresets, presetStripFor } from '../src/client/shell-presets.ts'
 import type { DesktopEnv } from '../src/client/desktop-env.ts'
 
+/** Resolve an i18n-friendly string-or-function value (mirror of textOf).
+ *  Preset descs went through the same union as the plugin catalog's texts,
+ *  so they resolve through t() in the active (test: en) locale. */
+function textOf(value: string | (() => string)): string {
+  return typeof value === 'function' ? value() : value
+}
+
 const env = (partial: Partial<DesktopEnv>): DesktopEnv => ({
   desktop: false,
   mode: null,
@@ -25,7 +33,8 @@ describe('shell presets', () => {
       expect(ids.has(preset.id)).toBe(false)
       ids.add(preset.id)
       expect(preset.title.length).toBeGreaterThan(0)
-      expect(preset.desc.length).toBeGreaterThan(0)
+      // Descs are i18n-friendly now (string or () => string) — resolve first.
+      expect(textOf(preset.desc).length).toBeGreaterThan(0)
       // The strip function must be total — an unknown environment yields
       // undefined, never a throw.
       expect(() => presetStripFor(preset, env({ desktop: false, mode: null, platform: null }))).not.toThrow()