When display.cleanup_progress (or display.platforms.<plat>.cleanup_progress)
is true, the gateway deletes tool-progress bubbles, long-running '⏳ Still
working...' notices, and status-callback messages after the final response
is delivered successfully. Currently effective on adapters that implement
delete_message (Telegram); silently no-ops elsewhere. Off by default.
Failed runs skip cleanup so bubbles stay as breadcrumbs.
Minimal plumbing: base.py's existing post_delivery_callback slot now chains
new registrations onto any existing callback (with per-callback exception
isolation) rather than clobbering. Stale-generation registrations are
rejected so they can't step on a fresher run's callbacks. This lets the
cleanup callback coexist with the background-review release hook already
registered on the same slot.
Co-authored-by: mrcharlesiv <Mrcharlesiv@gmail.com>
