Adds new_show() that inserts a NEW SHOW marker into Devon's history
so he won't reference previous episodes' callers or topics, trims
older history while keeping some long-term memory, and clears
research_cache + pending suggestions. Buffered suggestions are now
tracked in history via _track_suggestion() so Devon won't suggest
the same thing twice. Devon history scoped to current show on ask.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>