erlang: fold lists/proplists BIFs into transpile.sx + runtime.sx (completes 27dedf9b)

27dedf9b deleted lists-ext.sx but a botched git-add left the actual
fold-in unstaged, so HEAD briefly referenced functions that weren't
registered. This commit lands them:

- transpile.sx: function bodies appended next to existing er-bif-lists-*
- runtime.sx: registrations inside er-register-builtin-bifs!
- conformance.sh: drop the lists-ext.sx load; keep the lists_ext suite

Conformance 874/874 (verified on the combined tree before push).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/erlang/conformance.sh

@@ -51,7 +51,6 @@ cat > "$TMPFILE" << 'EPOCHS'
 (load "lib/erlang/parser-module.sx")
 (load "lib/erlang/transpile.sx")
 (load "lib/erlang/runtime.sx")
-(load "lib/erlang/lists-ext.sx")
 (load "lib/erlang/tests/tokenize.sx")
 (load "lib/erlang/tests/parse.sx")
 (load "lib/erlang/tests/eval.sx")