feat(#2038): hint matrix bridge errors may be a daemon restart

hive-matrix-mcp/src/bin/mcp.rs

@@ -35,9 +35,13 @@ use hive_matrix_mcp::protocol::{DaemonOp, DaemonRequest, DaemonResponse, InviteA
 /// a single round-trip) so connection pooling would be over-engineering.
 async fn round_trip(req: DaemonRequest) -> Result<DaemonResponse> {
     let socket = paths::daemon_socket();
-    let stream = UnixStream::connect(&socket)
-        .await
-        .with_context(|| format!("connect daemon socket {}", socket.display()))?;
+    let stream = UnixStream::connect(&socket).await.with_context(|| {
+        format!(
+            "matrix daemon unreachable at {} — it may be starting up or restarting \
+             (the daemon rebinds its socket a few seconds after a restart); retry shortly",
+            socket.display()
+        )
+    })?;
     let (reader, mut writer) = stream.into_split();
     let mut line = serde_json::to_string(&req)?;
     line.push('\n');