Summary

Fixes Desktop Enter-key handlers so Enter used to commit IME composition does not also trigger submit/save actions.

This is a narrow macOS/CJK input quality fix and does not overlap with the larger Desktop i18n/localization work.

Changes

• Add isImeComposing() helper for KeyboardEvent.isComposing plus legacy keyCode === 229
• Apply it to:
  • main chat composer submit path
  • message edit composer submit path
  • onboarding API key / OAuth code inputs
  • session rename input

Why

Chinese/Japanese/Korean IMEs use Enter to commit the current candidate. Without this guard, Hermes Desktop can submit or save while the user is still composing text.

Test plan

• macOS: enable a Chinese/Japanese/Korean IME
• In the chat composer, type a preedit string and press Enter to commit candidate; message should remain in the composer
• Press Enter again after composition ends; message should submit normally
• Repeat for message edit mode, onboarding code/API-key inputs, and session rename

Fixes #37483