Gleam 1.19 uses Erlang abstract forms for faster builds

Gleam 1.19 now generates Erlang abstract forms rather than Erlang source, skipping the front end of the Erlang compiler and improving build times. The change also records runtime location metadata against original Gleam code, making BEAM crash reports and stacktraces more accurate.

The release additionally flattens JavaScript decision trees, optimises short list literals, preserves generics in TypeScript variant checks, and adds language-server support for labels.