Fix false positive: Struct.new(keyword_init: true) members are optional

[apiology]

Summary

solargraph typecheck --level strong treated every member of a Struct.new(..., keyword_init: true)-generated class as a required keyword argument, reporting a false "Missing keyword argument" error when a call site omitted one. At runtime, keyword_init: true Struct members default to nil when omitted, exactly like ordinary Struct.new(...) members.

lib/solargraph/convention/struct_definition.rb generated Pin::Parameter pins for keyword-init Struct members with decl: :kwarg (required). Changed to decl: :kwoptarg (optional), matching how TypeChecker#parameterized_arity_problems_for already distinguishes required (:kwarg) from optional (:kwoptarg) keyword parameters.

Data.define (lib/solargraph/convention/data_definition.rb) is untouched ��� its members genuinely are required at runtime, so :kwarg stays correct there.

class Watch < Struct.new(:name, :time, keyword_init: true); end

class Caller
  # @return [Watch]
  def go
    Watch.new(name: 'foo') # no longer flagged as missing `time:`
  end
end

Fixes #1268

Test plan

• Added spec asserting keyword-init Struct parameters have decl == :kwoptarg
• Added typecheck spec reproducing the issue's exact repro, asserting no "Missing keyword argument" problem
• bundle exec rspec (full suite): 1626 examples, 0 failures
• bundle exec rubocop on changed files: no offenses
• Manually ran solargraph typecheck --level strong against the issue's repro: 0 problems found (previously reported the false positive)

���� Generated with Claude Code

https://claude.ai/code/session_01TqwAY5yf6K1ZQdYoSZDkmy