Reject surviving parameter decorators after transforms

Add a Program-owned validation pass that walks the final AST and reports TS1206 once per decorated parameter, using the full decorator-list span for the diagnostic range.

Invoke that validation from compile after transforms have had their afterInitialize window, so transformers can still remove parameter decorators before any diagnostics are emitted.

Add a dedicated compiler rejection fixture covering regular, rest, explicit-this, constructor-property, function-type, function-expression, and arrow-parameter cases.

Author: jtenner

src/compiler.ts

@@ -536,6 +536,7 @@ export class Compiler extends DiagnosticEmitter {
 
     // initialize lookup maps, built-ins, imports, exports, etc.
     this.program.initialize();
+    this.program.validateParameterDecorators();
 
 
     // Binaryen treats all function references as being leaked to the outside world when