Add setting to persist editor mode (vim) across sessions

Summary

The /vim command enables vim-style editing in the Claude Code input, which is great for vim users. However, this setting is session-only and must be re-enabled every time Claude Code is started.

Request

Add a setting (e.g., preferredEditorMode) to ~/.claude/settings.json that allows users to set their preferred editor mode permanently.

Proposed Implementation

{
  "preferredEditorMode": "vim"
}

Possible values: "default", "vim", "emacs" (if supported)

Current Workaround

Run /vim at the start of each session.

Why This Matters

Users who prefer vim keybindings have muscle memory that makes the default editor feel awkward. Having to remember to run /vim each session adds friction to the workflow.