feat(call-to-play)!: coordinate game sessions across peers

Implement the launcher design as a production peer-to-peer feature. Call to
Play actions are immutable, validated events broadcast over the existing QUIC
control channel, deduplicated in a bounded in-memory history, and exchanged in
Hello/HelloAck so late joiners reconstruct current calls.

Add the Tauri bridge and modular launcher surfaces for play-now and scheduled
calls, check-in, readiness buffers, role-aware controls, chat, tickers, and
actual caller launch. A deterministic frontend reducer derives presentation
state from replicated history. Extend the JSONL peer harness with publish/list
commands and a three-peer live-delivery and late-join scenario.

This intentionally raises the only supported wire protocol from version 5 to
version 6; older builds are not supported. Document the transport architecture
and exclude generated peer-test state from Docker build contexts.

Test Plan:
- `just fmt` -- passed
- `just clippy` -- passed
- `just test` -- passed
- `just frontend-test` -- passed, 20 tests
- `just build` -- passed
- `just peer-cli-tests S2 S48` -- passed
- `git diff --cached --check` -- passed

crates/lanspread-peer/ARCHITECTURE.md

@@ -44,6 +44,21 @@ When a peer is discovered:
 - Any message updates `last_seen`.
 - Pings run only when idle (or on a longer interval), not every 5 seconds.
 - Library updates are pushed as deltas, debounced and coalesced.
+- Call to Play actions are broadcast as immutable, uniquely identified events.
+
+### Call to Play replication
+
+Call to Play is transient peer-session state rather than database state. The
+peer keeps a bounded event history, deduplicated by event ID. 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.
+
+`Hello` and `HelloAck` include each side's event history. This lets peers that
+join after a call was created reconstruct the same nominations, responses,
+RSVPs, chat, and terminal actions. The launcher reducer sorts the event stream
+deterministically and derives deadlines and check-in phases from timestamps.
+There is deliberately no compatibility path for older protocol versions.
 
 ### 4) Shutdown