Fix unresolved method-level generic block parameters

[apiology]

This PR was written by Claude Code on behalf of @apiology.

Problem

Enumerable#each_with_object is typed in core RBS as:

[U] (obj U) { [U] (arg_0 Elem, obj U) -> untyped } -> U

U is a method-level generic bound by the obj argument passed to each_with_object. Inside the block, arg_0 (typed Elem, the receiver's own generic) resolves correctly, but obj (typed U) resolves to no type at all:

class Repro
  # @return [void]
  def scratch
    # @type [Array<Integer>]
    arr = [1, 2, 3]
    arr.each_with_object({}) { |e, memo| memo[e] = e }
  end
end

solargraph typecheck --level strong reports Unresolved call to []= on memo. The same shape of bug affects any method with a method-level generic bound via an argument passed alongside a block, e.g. Enumerable#inject.

Root cause

Pin::Callable#resolve_generics_from_context resolves a method-level generic from the method's own argument types into a shared resolved_generic_values hash, then recurses into the yielded block's parameter list to resolve that signature too. That recursive call is made with no per-parameter argument types available (nil), and the code took a shortcut for that case: it dup'd each block parameter instead of running it through resolve_generics_from_context. So even though resolved_generic_values["U"] was already populated from the method's own obj argument, the block's own obj parameter (typed generic<U>) never picked it up.

Fix

Always route block parameters through resolve_generics_from_context, passing arg_types&.[](i) instead of skipping resolution when arg_types is nil. ComplexType::UniqueType#resolve_generics_from_context already handles a nil context type by falling back to resolved_generic_values[type_param] || self, so this is a pure bug fix with no behavior change for the case where argument types are available.

Testing

Added spec cases in spec/source_map/clip_spec.rb covering each_with_object, inject, and a negative control (each_with_index, which has no method-level generic in its block signature and must be unaffected). Full suite: 0 failures.