Quote host names in DOT output

Wrap host identifiers with quotes when generating Graphviz DOT to avoid invalid identifiers if hostnames contain punctuation or spaces. Updated node declaration and both producer/consumer edges to use %q for host formatting in internal/streams/dot.go; other fields (IDs, labels, titles) remain unchanged.

internal/streams/dot.go

@@ -111,12 +111,12 @@ type conn struct {
 
 func (c *conn) appendDOT(dot []byte, group string) []byte {
 	host := c.host()
-	dot = fmt.Appendf(dot, "%s [group=host];\n", host)
+	dot = fmt.Appendf(dot, "%q [group=host];\n", host)
 	dot = fmt.Appendf(dot, "%d [group=%s, label=%q, title=%q];\n", c.ID, group, c.FormatName, c.label())
 	if group == "producer" {
-		dot = fmt.Appendf(dot, "%s -> %d [label=%q];\n", host, c.ID, humanBytes(c.BytesRecv))
+		dot = fmt.Appendf(dot, "%q -> %d [label=%q];\n", host, c.ID, humanBytes(c.BytesRecv))
 	} else {
-		dot = fmt.Appendf(dot, "%d -> %s [label=%q];\n", c.ID, host, humanBytes(c.BytesSend))
+		dot = fmt.Appendf(dot, "%d -> %q [label=%q];\n", c.ID, host, humanBytes(c.BytesSend))
 	}
 
 	for _, recv := range c.Receivers {