fix: make the yosys templates and synth.sh work for all three flows

• templates take {{CONVERTER}}, {{CONV_FLAGS}} and {{CASE_DIR}} instead of a hardcoded converter and {{OUT_DIR}}/{{BASE_NAME}}
• synth.sh picks convert_bbdd, convert_bdd or convert_muxig_opt per option (options 2 and 3 used to run convert_bbdd)
• bdd template: select {{TOP_MODULE}}_bdd, run abc on the copy only
• read the liberty as blackboxes so ltp reports real path lengths
• write each netlist from an isolated design copy
• convert_muxig_opt honours -o for its netlist; muxig uses python3

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>