Keep complete running and cancelled histories visible for fifteen minutes so
peers retain the roster, chat, and outcome long enough to understand what
happened. Compact them to terminal tombstones afterward without charging
settled calls against the active-history limit.
Model running and cancelled as durable read-only frontend states, exclude
them from active badges, prune retired raw events, and document the lifecycle.
Add peer scenario S49 to prove a late joiner reconstructs a terminal call with
its roster and chat intact.
Test Plan:
- just fmt
- just clippy
- just test
- just frontend-test
- just build
- just peer-cli-tests S48 S49
- python3 -m py_compile crates/lanspread-peer-cli/scripts/run_extended_scenarios.py
- git diff --cached --check