Hide the auto-generated Struct initialize when the block defines its own

[sjh9714]

Summary

Fixes #458.

Struct.new(:x, :y) do def initialize(x = 0, y = 0); super; end end emitted
two def initialize: lines — the auto-generated (Integer, Integer) -> void
and the user-defined (?Integer, ?Integer) -> void — so the generated RBS
fails rbs validate with RBS::DuplicatedMethodDefinitionError.

A method defined in the block body overrides the auto-generated one, so
dump_declarations now skips a StructNewNode-synthesized entry when the
block body defines a method with the same name (checked via a new
StructNewNode#block_defines_method?, which ignores defs belonging to nested
classes inside the block). The guard also covers block overrides of member
readers/writers, and Data.define shares the same path.

The synthesized method box itself stays installed: super in the user's
initialize resolves to the untyped stdlib Struct#initialize, and the
synthesized box is what carries Pt.new(3, 4) argument types into the member
ivars, so removing it would degrade def x: -> Integer to untyped.

One limitation left as is: def self.[] keeps the member-based signature
rather than mirroring the user-defined initialize (the issue's expected
output shows the mirrored form). That needs [] to reuse the user
initialize's formal arguments and looks like a separate inference
improvement.

Changes

• lib/typeprof/core/ast/meta.rb: add StructNewNode#block_defines_method?
• lib/typeprof/core/service.rb: skip shadowed synthesized method entries in
  dump_declarations
• scenario/misc/struct_new.rb: regression scenario from the issue repro
  (fails before the fix with exactly the duplicated line from the report)

Testing

• bundle exec ruby test/scenario_test.rb -n "/struct_new/"
• bundle exec rake test (433 tests, 830 assertions, 0 failures)
• rbs -I out.rbs validate on the output generated from the issue's script
  now exits 0

[mame]

Thanks! I'll merge this for now.

That said, I don't think it fully fixes #458. As pointed out in #458 (comment), Dog#age is inferred as String where it should be Integer, and that part doesn't look easy to fix.