lowering: matching Some/None pulls in the Option classes

[simontreanor]

Fixes #25.

needs_option decides whether the runtime import (project build) or the inlined Option prelude (single file) is emitted, and only construction sites set it. lower_pattern''s Pattern::Ctor arm sets needs_result for Ok/Error but had no matching line for Some/None, so a module that merely consumed an Option emitted case None_(): with nothing defining or importing that name — NameError at runtime, after check and compile both passed.

Cross-module is where this is easy to hit, because the producer lives in the other file:

NameError: name ''None_'' is not defined. Did you mean: ''None''?

But it was never really about modules. A single file that only matches — a function whose Option arrives as a parameter — emitted the same broken output on main:

def probe(o):
    match o:
        case None_():        # nothing defines None_
            return "none"
        case Some(k):
            return k

Fix

Set needs_option for Some/None in the constructor-pattern arm, mirroring the Ok/Error line directly above it.

Tests

• tests/compile.rs::matching_an_option_pulls_in_the_option_prelude — the single-file case.
• tests/project.rs::a_module_that_only_matches_an_imported_option_imports_it — the cross-module case: asserts the from _pyfun_rt import Some, None_ header and runs the program end to end.

Both verified to fail on main. cargo test green, cargo clippy --all-targets clean, cargo fmt applied.