Allow customisation of Umbral companion personality from the CLI

Feature Request

It should be possible to customise the Umbral companion's personality (tone, style, content) from the Claude Code command line or settings, without requiring code changes.

Use case

Users want to tailor Umbral's speech bubble style — e.g. more haiku, more terse warnings, a different persona — to match their preferences and workflow.

Suggested approach

A setting in settings.json or a CLI flag such as --companion-personality that accepts a short prompt/description, e.g.:

{
  "companion": {
    "personality": "Speaks only in haiku. Always nature-themed."
  }
}

Current behaviour

Umbral's personality is fixed and cannot be changed by the user.

🤖 Submitted via Claude Code