The `Parameter` kind in `UntypedKind` was only used for identifiers that
were being declared or referenced. This commit renames it to
`Identifier` and updates all the necessary code to reflect this change.
This simplifies the AST and makes it more consistent.
Additionally, a new macro `repeat` has been added to
`src/ast/system.myc`.
- Add `rtl/system.myc` as the system library, containing core utilities
like `while` and `cache`.
- Remove the duplicate `prelude.myc` from `src/ast/rtl/`.
- Modify `Environment::collect_dependencies` to implicitly add `#use
system` when necessary.
- Update `Environment::with_cwd` to also add the `rtl` subdirectory to
search paths.
- Add `target/` to `.geminiignore` to exclude build artifacts.
- Adjust example `sma.myc` to use the new `cache` macro and reduce
sample data size.
- Update `rtl/sma.myc` to correctly initialize the `history` series with
its `length`.
- Add `preload_dependencies` calls to `dump_ast` and `run_script` for
proper module loading.