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.

src/client/SideCardSection.tsx

@@ -947,9 +947,11 @@ export function SideCardSection({ store, service }: SideCardSectionProps) {
                 ...getShellPresets().map(preset => ({
                   value: `preset:${preset.id}`,
                   title: preset.title,
+                  // The preset desc is i18n-friendly (string or () => string)
+                  // — resolve it like every other settings text here.
                   desc: preset.detect?.(detectedEnv) === true
-                    ? `${preset.desc}（${t('settingsSchemeDetectedSuffix')}）`
-                    : preset.desc,
+                    ? `${textOf(preset.desc)}（${t('settingsSchemeDetectedSuffix')}）`
+                    : textOf(preset.desc),
                 })),
                 { value: 'custom', title: t('settingsSchemeCustomTitle'), desc: t('settingsSchemeCustomDesc') },
               ]}