Address PR feedback: sigil fix and cleanup

- Change `.capture_flamegraph?` to `#capture_flamegraph?` (instance method)
- Remove temp directory setup (now handled globally via spec_helper)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: dpep

spec/singed/middleware_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "tmpdir"
-
 describe Singed::RackMiddleware do
   subject do
     instance.call(env)
@@ -12,11 +10,6 @@
   let(:env) { Rack::MockRequest.env_for("/", headers) }
   let(:headers) { {} }
 
-  before do
-    allow_any_instance_of(Singed::Flamegraph).to receive(:open)
-    Singed.output_directory = Dir.mktmpdir("singed-spec")
-  end
-
   it "returns a proper rack response" do
     linted_app = Rack::Lint.new(instance)
     expect { linted_app.call(env) }.not_to raise_error
@@ -28,15 +21,23 @@
   end
 
   context "when enabled" do
-    before { allow(instance).to receive(:capture_flamegraph?).and_return(true) }
+    before do
+      allow_any_instance_of(Singed::Flamegraph).to receive(:open)
+      allow(instance).to receive(:capture_flamegraph?).and_return(true)
+    end
 
     it "captures a flamegraph" do
       expect(instance).to receive(:flamegraph).and_call_original
       subject
     end
+
+    it "returns a proper rack response" do
+      linted_app = Rack::Lint.new(instance)
+      expect { linted_app.call(env) }.not_to raise_error
+    end
   end
 
-  describe ".capture_flamegraph?" do
+  describe "#capture_flamegraph?" do
     subject { instance.capture_flamegraph?(env) }
 
     it { is_expected.to be false }