Fix lockfile requirement preservation and orphaned deps test

Preserve the original dependency requirement from root deps when
building ActivationRequests, so lockfiles correctly record constraints
like "a (>= 1)" instead of bare "a".

Update the orphaned dependencies test: PubGrub correctly backtracks
from b-2 (missing c-2) to b-1 (has c-1), finding a valid solution
that Molinillo's simpler backtracking missed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: mlarraz

lib/rubygems/resolver.rb

@@ -171,10 +171,12 @@ def resolve
     result = solver.solve
 
     # Convert to Array<ActivationRequest>
+    needed_by_name = @needed.group_by(&:name)
     result.filter_map do |package, version|
       next if Gem::PubGrub::Package.root?(package)
       spec = spec_for(package.to_s, version)
-      dep_request = DependencyRequest.new(Gem::Dependency.new(package.to_s), nil)
+      dep = needed_by_name[package.to_s]&.first || Gem::Dependency.new(package.to_s)
+      dep_request = DependencyRequest.new(dep, nil)
       ActivationRequest.new(spec, dep_request)
     end
   rescue Gem::PubGrub::SolveFailure => e

test/rubygems/test_gem.rb

@@ -328,13 +328,9 @@ def test_activate_bin_path_raises_a_meaningful_error_if_a_gem_thats_finally_acti
 
     install_specs c1, b1, b2, a1
 
-    # c2 is missing, and b2 which has it as a dependency will be activated, so we should get an error about the orphaned dependency
-
-    e = assert_raise Gem::UnsatisfiableDependencyError do
-      load Gem.activate_bin_path("a", "exec", ">= 0")
-    end
-
-    assert_equal "Unable to resolve dependency: 'b (>= 0)' requires 'c (= 2)'", e.message
+    # c2 is missing, but the resolver backtracks from b2 to b1 which
+    # works with c1, finding a valid solution despite partial installation
+    load Gem.activate_bin_path("a", "exec", ">= 0")
   end
 
   def test_activate_bin_path_in_debug_mode