Feature request: option to disable Companion (Clatter)

Summary

Please add a setting to disable the Companion feature (the small mushroom named Clatter that appears in the input box).

Motivation

Some users prefer a cleaner interface without the Companion. Currently there is no documented or undocumented way to disable it — neither via settings.json fields nor environment variables. Attempts to add "companion": false or "enableCompanion": false to ~/.claude/settings.json are rejected by the schema validator.

Proposed Solution

Add a boolean field to the settings schema, for example:

{
  "companionEnabled": false
}

Or alternatively expose it as an environment variable:

CLAUDE_COMPANION_ENABLED=false

Current Behavior

No way to disable the Companion. Schema validation rejects unrecognized fields.

Expected Behavior

Setting companionEnabled: false (or equivalent) hides the Companion from the UI.