inferExprType now returns .unresolved when it genuinely cannot infer a type,
instead of silently guessing .s64. To keep codegen correct, every consumer
that turns inference into a concrete type was fixed to resolve it properly
rather than lean on the fake s64:
- pack-fn mono: value-pack params type from the lowered Ref (getRefType);
comptime ..$args prefers inference (int-literal default is s64) and falls
back to the lowered type only when inference cannot tell.
- if-expr / match merge result type: fall back to the contextual target_type
when the branch/arm type is not statically inferable; a statement match with
non-value arms stays void (do not let a leaked target_type make it a value).
- inferExprType call arm: resolve a not-yet-lowered function return type from
fn_ast_map (void for a return-less fn) instead of falling through.
- lowerBinaryOp: type the result from the lowered LHS when inference is
unresolved (e.g. #objc_call(...) * 2).
- null comparison (x == null): lower the non-null side first and take the
null type from it, never a guess.
A consequence: `xx enum` with no target type now boxes as Any (prints the
variant name) instead of the silent-s64 int -- examples/52 snapshot updated to
the honest output. 236 examples + unit tests green.
