Summary

This PR does two things in the same pass:

1. Adds a persisted display-language setting and broad Simplified Chinese (zh-CN) UI localization across Warp OSS.
2. Reconciles the local localization work with a large set of upstream behavior changes so the branch remains buildable and testable on top of the newer codepaths.

What changed

• Added display-language settings support and i18n plumbing:

  • introduced app/src/i18n.rs
  • introduced app/src/settings/language.rs
  • registered the language setting in settings initialization
  • localized menu labels, settings surfaces, auth flows, toasts, dialogs, and many common UI actions

• Expanded Chinese coverage across the app:

  • top-level app menus and menu actions
  • Settings navigation and Appearance language selector
  • auth/sign-in and onboarding flows
  • agent management, AI chrome, notebook/workflow/drive surfaces
  • terminal context menus, shared-session controls, and many toast/error states

• Synced several upstream behavior chains needed for the branch to stay healthy:

  • cloud-mode-v2 slash command flow
  • ambient agent follow-up and host/harness/environment selector plumbing
  • remote server preinstall/version-compatibility support path
  • execution-profile and AI-settings denylist/list-row behavior
  • pending remote session handling in workspace/file-tree/global-search
  • pane header / orchestration pill bar support path

Notes

• This is not a pure string-only PR. It includes settings/UI behavior wiring required to support the new language feature and to preserve compatibility with upstream changes.
• The main runtime-facing addition is the display-language setting plus the broad UI localization.
• Several upstream support files were pulled in to keep the branch compiling after syncing behavior from newer remote changes.

Validation

Ran:

• cargo fmt --all
• cargo check -p warp
• cargo test -p warp i18n::tests::all_i18n_keys_have_non_empty_catalog_entries
• git diff --check

Follow-ups

• Some newly synced orchestration-related codepaths still produce compile warnings for currently-unused breadcrumb/pill-bar helpers. They do not block build/test, but may be worth cleaning up in a follow-up.
• There may still be intentionally untranslated technical strings (commands, filenames, regex examples, etc.) left in English by design.