parse: reserved names not enforced for nested types and oneofs

[JavaGT]

Lane: reflection/parse (sweep 2, finding 3)
Reserved names are enforced only for fields (src/type.js:412-415); oneofs check only the $ prefix (src/type.js:426-436) and Namespace.prototype.add (src/namespace.js:267-316) never consults reserved names — nested messages/enums with a reserved name are accepted.

Repro (executed): both accepted, protoc rejects:

pb.parse('syntax = "proto2"; message M { reserved "foo"; message foo {} }');
pb.parse('syntax = "proto2"; message M { reserved "foo"; oneof foo { int32 a = 1; } }');

Verdicts: both Confirm, Worth exploring (pedantic class).

Upstream: protobufjs#1284/protobufjs#1883 are enum-reserved topics, not this gap.

Decision question: Adopt (extend reserved-name checks to nested namespaces and oneofs) or Reject as pedantic?