feat(i18n): add translatable plugin name and description

[ZacharyZcR]

Adds plugin.description (and plugin.name where it was missing) to the plugin's locales so Termix can show the description in the user's language, the same way it already shows plugin.name. The English text is the manifest description. zh_CN and zh_TW are included, and other languages are filled in by the release translation step.

Core side: Termix reads plugin.description and falls back to the manifest description when it is missing.

[termix-triage-bot]

AI review | Looks safe to merge

Adds translatable name and description keys to the English locale file. The change is limited to static text and follows the plugin localization rules.

_{Reviewed 2ac3c6c. AI can be wrong, a maintainer still decides. Comment /termix review to run it again.}