fixes #14825

What it does

• Localize AI Agent Descriptions
• Localize AI Preferences
• Localize AI View Titles and Descriptions
• Localize AI Commands and Menus

The following have NOT been localized:

• Agent Names
  • I'm not sure which part of the Agent is used as a regular label, and which is used to actually call the @Agent; so I let agent Names as-is
• React Contents
  • I'm not sure how to best provide localization for a mix of Text, HTML and overall React magic, so I skipped everything in *.tsx
• Prompt Templates
  • This seems complicated and risky. Especially, a lot of Prompt Templates use JS-template strings with variables, so it would be a significant effort to localize properly
• Errors/Warnings
• Progress Messages

The PR only includes Typescript changes (nls.localize()). NLS files have not been updated, for any language.

How to test

The PR only introduces nls.localize() calls, so it can't immediately be tested. I'm not sure what is the best way to test the changes, but what I did:

• Add (a subset of) the keys to your favorite language, in packages/core/i18n/nls.**.json

For example, in French:

"theia": {
    "ai": {
      "chatUi": {
        "attachToContext": "Ajouter des éléments au contexte",
        "cancel": "Annuler (Esc)",
        "removeChat": "Supprimer la conversation",
        "send": "Envoyer (Enter)"
      }
    },

• Start Theia
• In the Command Palette, call Configure Display Language and select the modified language
• Restart Theia Frontend
• Check that the localized messages properly appear

Follow-ups

Breaking changes

• This PR introduces breaking changes and requires careful review. If yes, the breaking changes section in the changelog has been updated.

Attribution

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines