Desktop app: option to make Enter insert a newline and submit only via click / Ctrl+Enter

## Feature request

In the Claude desktop app (Code tab), pressing Enter in the chat composer submits the message. Users who type longer, multi-paragraph prompts frequently submit unfinished messages by accident.

### Requested behavior

A setting (or support for `~/.claude/keybindings.json` in the desktop app's chat composer) so that:

- Enter inserts a newline, and
- the message is submitted only by clicking the send button or via a dedicated key combination (e.g. Ctrl+Enter).

Other chat clients offer this as a user preference ("Enter sends" on/off).

### Current state

- The CLI supports remapping via `keybindings.json` (`chat:submit` / `chat:newline`), per https://code.claude.com/docs/en/keybindings.
- It is not documented whether the desktop app's Code tab honors that file, and there is no visible setting for it in the app.

### Environment

- Claude desktop app, Code tab, Windows 11

Start by checking whether the Claude desktop app's Code tab reads ~/.claude/keybindings.json and review the documented chat:submit and chat:newline mappings. No repository file or entry point is named in the issue. Done would be a documented or visible setting that makes Enter insert a newline while click or Ctrl+Enter submits the message.

Written by the indexing model from the issue text.