Fix @yieldparam type lost on multi-overload block-form methods

[apiology]

Summary

Fixes #1289.

Pin::Method#generate_signature always read @yieldparam/@yieldreturn tags from the method's own docstring, even when it was building the Signature for an @overload tag. Per YARD, @overload docstrings are self-contained, so when a method declared a block-form @overload alongside a second, plain @overload, the block-form overload's @yieldparam was silently dropped — the block-local variable resolved as untyped at the call site.

generate_signature now takes the docstring to read those tags from, and #signatures passes each overload tag's own docstring instead of the method's.

# @overload build
#   @return [String]
# @overload build
#   @yieldparam widget [String]
#   @return [void]
def build
  return 'hi' unless block_given?
  yield 'hi'
end

build do |w|
  w.upcase # was: Unresolved call to upcase
end

Test plan

• bundle exec rspec (1443 examples, 0 failures)
• bundle exec rubocop on changed files (clean)
• Manually confirmed solargraph typecheck --level strong on the issue's repro now reports 0 problems

[apiology]

🤖 Filed by Claude, not Vince — acting on his credentials.

This fixes @yieldparam loss for YARD @overload-declared block-form methods, but our real-world case (Net::HTTP.start, an RBS-declared generic block-form overload) still fails on this branch — a different code path from the one this PR touches (Pin::Method#generate_signature/#signatures, YARD-only). Bisecting further: the failure is conditional on a keyword argument being present in the call. Net::HTTP.start('example.com') { |http| ... } (no kwargs) resolves http correctly; Net::HTTP.start('example.com', use_ssl: true) { |http| ... } does not. An equivalent plain YARD @generic/@yieldparam method (no RBS involved) is unaffected by adding a keyword arg to its call — so this looks specific to RBS generic-method-type translation, not a general kwarg-plus-block gap.

require 'net/http'

Net::HTTP.start('example.com', use_ssl: true) do |http|
  http.request(Net::HTTP::Get.new('/'))
end

$ bundle exec solargraph typecheck --level strong repro.rb
repro.rb:4: Unresolved call to request

Dropping use_ssl: true (call with no keyword arg at all) makes this 0 problems found on the same branch.

[apiology]

🤖 Filed by Claude, not Vince — acting on his credentials.

Root cause isn't RBS-specific. Call#inferred_pins (lib/solargraph/source/chain/call.rb) matches call-site arguments to a signature's parameters purely by array index. A trailing keyword-arguments hash (use_ssl: true) is just another element in that array, so it gets checked against whatever positional parameter sits at that index — port here — instead of the kwrest parameter (**opt). The mismatch rejects the whole overload, so the block-form generic overload never matches and http falls back to untyped.

Confirmed this predates and is independent of this PR's 0b60c02e4 commit: it reproduces on master before that commit, and with a plain YARD **kwrest method that has no RBS involvement at all.

Fix and reproduction (matching the case above) are up at #1292.