Sonic -> Grok Code Fast

[mrubens]

Important

Renamed model from 'Sonic' to 'Grok Code Fast' across codebase, updating model IDs, default settings, and announcement texts in multiple languages.

• Model Renaming:
  • Rename model ID from roo/sonic to xai/grok-code-fast-1 in roo.ts and xai.ts.
  • Update default model ID to xai/grok-code-fast-1 in xai.ts.
• Functionality:
  • Modify shouldUseSingleFileRead() in single-file-read-models.ts to check for grok-code-fast-1.
  • Update getSelectedModel() in useSelectedModel.ts to handle new model ID.
• Announcements:
  • Update announcement texts in Announcement.tsx and Announcement.spec.tsx to reflect model renaming.
  • Modify latestAnnouncementId in ClineProvider.ts to aug-25-2025-grok-code-fast.
• Localization:
  • Update model-related texts in multiple language files under webview-ui/src/i18n/locales/ to reflect the new model name and details.

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[roomote]

Thank you for this PR renaming Sonic to Grok Code Fast! I've reviewed the changes and found several issues that need attention, particularly around type consistency and the context window description.