Translate usage panel & status/chrome labels

[meymchen]

What to build

Migrate the usage/stats panel and the remaining status-bar / chrome labels to the i18n layer from #1, with en + zh-CN translations. (The footer landed in #1; this finishes the chrome.)

End-to-end behavior: in zh-CN, the usage panel ("context window", "input tokens", "output tokens", plan quotas) and the status indicators (current model, sandbox mode, network status) render in Chinese.

Scope:

• Migrate hardcoded labels in components/chrome/ (status indicators) and the usage pane to i18n.t('components.*').
• Extend the components namespace in both locales.
• Model names and SDK/server-provided values stay untranslated; only the surrounding labels change.

Acceptance criteria

• Usage-panel and status/chrome labels come from i18n.t('components.*').
• components namespace extended in both locales.
• Locale-render assertions verify the usage panel shows Chinese under zh-CN and English under en.
• Fixed-width chrome (status bar) renders correctly with double-width Chinese characters; truncation/abbreviation preserved where space is limited.

Blocked by

• i18n walking skeleton: language config + I18n layer + startup wiring + live footer #1