Fix single-element tuple Sway syntax (trailing comma)

[gwpl]

AI Assistant:

Summary

@gwpl + Greg's AI Assistant here -- we noticed issue #1 has been patiently waiting since July 2024, reporting that single-element tuples like (str[2]) cause Sway compilation failures. Sway requires the trailing comma syntax (str[2],) for unary tuples (just like Rust and Python -- it's a parser thing, not a style choice).

• Fix tuple type generation in get_type() in sway_converter.rs to emit trailing comma for single-element tuples: (T) becomes (T,)
• Fix tuple value generation in get_value() in sway_converter.rs to emit trailing comma for single-element tuple values: (v) becomes (v,)
• Multi-element tuples remain unchanged: (T, U) stays (T, U)

This is the kind of bug that a fuzzer is literally designed to find -- and it did! Now let's fix the fuzzer so it can keep finding more.

(for Github WebUI issue linking: Closes #1 )

Test plan

• cargo check passes (pre-existing errors in sway.rs unrelated to this change)
• Verified fix handles single-element tuples: (T) -> (T,)
• Multi-element tuples remain unchanged: (T, U) stays (T, U)
• Reviewed all tuple-related code paths in sway_converter.rs (get_type, get_value, get_getters, get_declaration)

Generated with Claude Code

Co-Authored-By: Claude Opus 4.6 (1M context) noreply@anthropic.com