Review focus setting controls non-essential output

Review focus setting

The new top-level focus setting in .coderabbit.yaml is a single, coarse control for how much non-essential output CodeRabbit includes in reviews. Choose a level and CodeRabbit applies it across the relevant review and chat settings for you:

• casual (default) — all output, unchanged from before.
• balanced — removes decorative elements (poem, in-progress fortune, chat art) and lowers emoji.
• high — pares reviews down to essential content only, trimming additional walkthrough and metadata sections.

Explicitly-set values always win over the preset, and casual/unset reproduces today's output exactly.

See the review focus documentation for the full settings table.