Add comprehensive C# → WAT test suite and fix type mapping bugs in compiler pipeline

[Copilot]

Testing/Program.cs was missing, leaving the C#→WAT compilation pipeline untested. Running tests exposed several real bugs in MapSet.cs and RuleSet.cs that caused incorrect or empty WAT output for typed variables.

New: Testing/Program.cs

26 tests covering the full CDTk compilation pipeline (Tokens + Rules + WASM MapSet):

• Primitive types (int, long, float, double, bool)
• Arithmetic, control flow (if/else, while, for)
• Methods with params and return types, namespaces, comments, string literals

// Usage
var (passed, failed) = CRAB.Testing.TestProgram.RunAll();

Bug Fixes

RuleSet.cs

• FloatingPointType was a plain string rule without .Returns("type") — unlike IntegralType which has it — causing float/double keywords to never be captured in the AST.

// Before
public Rule FloatingPointType = "type:@KwFloat | type:@KwDouble";

// After
public Rule FloatingPointType = new Rule("type:@KwFloat | type:@KwDouble")
    .Returns("type");

MapSet.cs

Map	Before	After	Reason
IntegralType	"i32"	"{type}"	Hardcoded; blocked long→i64, ulong→i64
FloatingPointType	"f64"	"{type}"	Hardcoded; blocked float→f32
LocalVariableType	"{type}"	"{base}"	CDTk places the matched node in base, not type
LocalDeclaration	"{type} {declarators}"	"{modifier} {type}"	CDTk field-shifts when the optional modifier is absent, putting the type into modifier and declarators into type

Known Limitations (documented in tests)

Three CDTk parser-level issues are beyond the scope of these Map fixes and are documented in the relevant tests:

• Arithmetic initializer expressions (e.g. 4 * 7) are not emitted into function bodies
• else blocks are not wrapped in WAT (else …) due to IfStatement field shifting
• Method call (call $fn) is not emitted; invocation suffix is parsed but not propagated

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