style(sidecar): apply rustfmt

Format the sidecar source with `cargo fmt` so the new `cargo fmt --check`
CI gate passes on the first run. No behavior change.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0114TpmrNW4wNXsHq5CR72jQ

sidecar/src/main.rs

@@ -96,7 +96,11 @@ async fn main() -> anyhow::Result<()> {
 
             // Persist, then broadcast. `pong` and `ws.hello` are ephemeral chatter, not history.
             if ev.kind != "pong" {
-                let t = ev.value.get("t").and_then(|v| v.as_i64()).unwrap_or_else(now_ms);
+                let t = ev
+                    .value
+                    .get("t")
+                    .and_then(|v| v.as_i64())
+                    .unwrap_or_else(now_ms);
                 let text = ev.value.to_string();
                 if let Err(e) = event_store.insert_event(t, &ev.kind, &text).await {
                     tracing::warn!(error = %e, "failed to persist event");