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/src/identity.rs

@@ -6,6 +6,7 @@ use crate::state_paths::peer_id_path;
 
 pub const FEATURE_LIBRARY_DELTA: &str = "library-delta-v1";
 pub const FEATURE_LIBRARY_SNAPSHOT: &str = "library-snapshot-v1";
+pub const FEATURE_CALL_TO_PLAY: &str = "call-to-play-v1";
 
 pub fn load_or_create_peer_id(state_dir: &Path) -> eyre::Result<String> {
     let path = peer_id_path(state_dir);
@@ -28,5 +29,6 @@ pub fn default_features() -> Vec<String> {
     vec![
         FEATURE_LIBRARY_DELTA.to_string(),
         FEATURE_LIBRARY_SNAPSHOT.to_string(),
+        FEATURE_CALL_TO_PLAY.to_string(),
     ]
 }