feat(call-to-play): retain terminal outcomes

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

crates/lanspread-peer/ARCHITECTURE.md

@@ -52,13 +52,15 @@ Call to Play is transient peer-session state rather than database state. The
 peer keeps a bounded event history, deduplicated by event ID. Every event and
 chat message remains in the snapshot for the full lifetime of an active call,
 so a peer joining mid-call receives the complete context. A creator's `Start`
-or `Cancel` event replaces that terminal call with one small tombstone; this
-lets a peer that missed the live action heal on its next handshake without
-retaining the inactive call's full history. Active calls are never partially
-trimmed. If genuinely active history reaches the bound, local publishes return
-an error to the caller instead of appearing to succeed. A call whose deadline
-elapses remains available for five minutes so the creator can start or extend
-it, then its history is evicted as a unit. A
+or `Cancel` makes the call terminal and read-only, but its complete roster and
+chat history remain in snapshots for 15 minutes so late joiners can see the
+outcome. After that display window the history compacts to the Start or Cancel
+tombstone for the rest of the peer session. Active and recently terminal calls
+are never partially trimmed. If genuinely active history reaches the bound,
+local publishes return an error to the caller instead of appearing to succeed;
+terminal histories and tombstones do not consume that active-history capacity.
+A call whose deadline elapses remains available for five minutes so the creator
+can start or extend it, then its unresolved history is evicted as a unit. A
 local action is applied to that history, sent to the UI, and broadcast to every
 currently known peer. An incoming live event is applied once and sent to the UI
 without being rebroadcast, which prevents forwarding loops.