Replace invalid default model IDs (e.g. claude-sonnet-4-7) with current
claude-sonnet-4-6, claude-opus-4-8, and claude-haiku-4-5. Route system
messages to the API system field, enable ephemeral prompt caching, omit
temperature for Opus 4.7/4.8, and surface cache usage metrics. Update the
CLI model picker to match.
Co-authored-by: Vladimir Đuranović <vlada@MacBook-Pro.local>
Co-authored-by: Cursor <cursoragent@cursor.com>