fix(jdk-codemodel, jdk-annotation-processor): complete constructor trait coverage across all three population paths

[deer]

• JdkInitializer (processConstructor): replaced the manual two-line wiring with resolver.modifyConstructor, which adds type parameters, throws declarations, access modifier, and annotations — bringing the source-based constructor path to parity with modifyMethod.
• TypeMirrorResolver: introduced modifyConstructor and widened addThrowables to accept any Traitable so it can serve both constructors and methods.
• JDKCodeModel (reflection path): fixed ThrowableDescriptor being attached to the type descriptor instead of the owning ConstructorDescriptor / MethodDescriptor; fixed getFormalParameters to attach Varargs and Final traits from java.lang.reflect.Parameter.
• AnnotationProcessor (createTypeDescriptor): added the missing CONSTRUCTOR element loop, matching the field and method loops that were already present.