Fix ABC9 sideband tests: add missing rename -enumerate

The ABC9 and Amaranth sideband invariant tests were missing the
`rename -enumerate` pass that the ABC sideband test already had.
Without it, JSON cells keep $abc$...-prefixed names while
write_verilog auto-generates _N_ names, causing a 31% match rate.

Co-developed-by: Claude Code v2.1.49 (claude-opus-4-6)

Author: robtaylor

.github/workflows/test-src-retention.yml

@@ -255,6 +255,7 @@ jobs:
           synth -top counter -flatten;
           abc9 -lut 4;
           autoname;
+          rename -enumerate;
           write_json abc9_sideband_output.json;
           write_verilog -noattr -noexpr abc9_sideband_output.nl.v;
           "
@@ -271,6 +272,7 @@ jobs:
           synth -top priority_enc -flatten;
           abc9 -lut 4;
           autoname;
+          rename -enumerate;
           write_json amaranth_sideband_output.json;
           write_verilog -noattr -noexpr amaranth_sideband_output.nl.v;
           "