[encoding] Fix bug in join estimate

The buffer size estimator wasn't accounting for the inner-join line
segments when counting joins. This resulted in an underestimate which
is particularly a problem when the scene content consists only of
line-tos (curves mask the problem since they are always over-estimated).

crates/encoding/src/estimate.rs

diff --git a/crates/encoding/src/estimate.rs b/crates/encoding/src/estimate.rs
index 92f0417..4aa4858 100644
--- a/crates/encoding/src/estimate.rs
+++ b/crates/encoding/src/estimate.rs
@@ -225,6 +225,10 @@
                 self.segments += count * arc_lines * count_segments_for_line_length(line_len);
             }
         }
+
+        // Count inner join lines
+        self.lines.linetos += count;
+        self.segments += count_segments_for_line_length(scaled_width) * count;
     }
 }