Enhance bin/dev kill to terminate processes on ports 3000 and 3001

Previously, `bin/dev kill` only terminated processes by pattern matching
(e.g., "rails", "puma", "webpack-dev-server"). This could miss processes
that were holding ports 3000 or 3001 but didn't match the patterns.

Now `bin/dev kill` also finds and terminates any process listening on
ports 3000 and 3001 using `lsof -ti:PORT`, ensuring a clean restart
even when unexpected processes are blocking the development ports.

Changes:
- Add kill_port_processes(ports) method to find and kill processes on specific ports
- Add find_port_pids(port) helper that uses lsof to find PIDs listening on a port
- Update kill_processes to call kill_port_processes([3000, 3001])
- Add comprehensive tests for port-killing functionality
- Handle edge cases (lsof not found, permission denied) gracefully

The port-killing is integrated as default behavior (no --force flag needed)
since ports 3000/3001 are explicitly development ports and this matches
the existing UX where kill doesn't ask for confirmation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: justin808

lib/react_on_rails/dev/server_manager.rb

@@ -27,7 +27,7 @@ def kill_processes
           puts "🔪 Killing all development processes..."
           puts ""
 
-          killed_any = kill_running_processes || cleanup_socket_files
+          killed_any = kill_running_processes || kill_port_processes([3000, 3001]) || cleanup_socket_files
 
           print_kill_summary(killed_any)
         end
@@ -75,6 +75,29 @@ def terminate_processes(pids)
           end
         end
 
+        def kill_port_processes(ports)
+          killed_any = false
+
+          ports.each do |port|
+            pids = find_port_pids(port)
+            next unless pids.any?
+
+            puts "   ☠️  Killing process on port #{port} (PIDs: #{pids.join(', ')})"
+            terminate_processes(pids)
+            killed_any = true
+          end
+
+          killed_any
+        end
+
+        def find_port_pids(port)
+          stdout, _status = Open3.capture2("lsof", "-ti", ":#{port}", err: File::NULL)
+          stdout.split("\n").map(&:to_i).reject { |pid| pid == Process.pid }
+        rescue StandardError
+          # lsof command not found or other error (permission denied, etc.)
+          []
+        end
+
         def cleanup_socket_files
           files = [".overmind.sock", "tmp/sockets/overmind.sock", "tmp/pids/server.pid"]
           killed_any = false

spec/react_on_rails/dev/server_manager_spec.rb

@@ -109,6 +109,10 @@ def mock_system_calls
       allow(Open3).to receive(:capture2)
         .with("pgrep", "-f", "bin/shakapacker-dev-server", err: File::NULL).and_return(["", nil])
 
+      # Mock lsof calls for port checking
+      allow(Open3).to receive(:capture2).with("lsof", "-ti", ":3000", err: File::NULL).and_return(["", nil])
+      allow(Open3).to receive(:capture2).with("lsof", "-ti", ":3001", err: File::NULL).and_return(["", nil])
+
       allow(Process).to receive(:pid).and_return(9999) # Current process PID
       expect(Process).to receive(:kill).with("TERM", 1234)
       expect(Process).to receive(:kill).with("TERM", 5678)
@@ -117,6 +121,22 @@ def mock_system_calls
       described_class.kill_processes
     end
 
+    it "kills processes on ports 3000 and 3001" do
+      # No pattern-based processes
+      allow(Open3).to receive(:capture2).with("pgrep", any_args).and_return(["", nil])
+
+      # Mock port processes
+      allow(Open3).to receive(:capture2).with("lsof", "-ti", ":3000", err: File::NULL).and_return(["3456", nil])
+      allow(Open3).to receive(:capture2).with("lsof", "-ti", ":3001", err: File::NULL).and_return(["3457\n3458", nil])
+
+      allow(Process).to receive(:pid).and_return(9999)
+      expect(Process).to receive(:kill).with("TERM", 3456)
+      expect(Process).to receive(:kill).with("TERM", 3457)
+      expect(Process).to receive(:kill).with("TERM", 3458)
+
+      described_class.kill_processes
+    end
+
     it "cleans up socket files when they exist" do
       # Make sure no processes are found so cleanup_socket_files gets called
       allow(Open3).to receive(:capture2).and_return(["", nil])
@@ -130,6 +150,59 @@ def mock_system_calls
     end
   end
 
+  describe ".find_port_pids" do
+    it "finds PIDs listening on a specific port" do
+      allow(Open3).to receive(:capture2).with("lsof", "-ti", ":3000", err: File::NULL).and_return(["1234\n5678", nil])
+      allow(Process).to receive(:pid).and_return(9999)
+
+      pids = described_class.find_port_pids(3000)
+      expect(pids).to eq([1234, 5678])
+    end
+
+    it "excludes current process PID" do
+      allow(Open3).to receive(:capture2).with("lsof", "-ti", ":3000", err: File::NULL).and_return(["1234\n9999", nil])
+      allow(Process).to receive(:pid).and_return(9999)
+
+      pids = described_class.find_port_pids(3000)
+      expect(pids).to eq([1234])
+    end
+
+    it "returns empty array when lsof is not found" do
+      allow(Open3).to receive(:capture2).and_raise(Errno::ENOENT)
+
+      pids = described_class.find_port_pids(3000)
+      expect(pids).to eq([])
+    end
+
+    it "returns empty array on permission denied" do
+      allow(Open3).to receive(:capture2).and_raise(Errno::EACCES)
+
+      pids = described_class.find_port_pids(3000)
+      expect(pids).to eq([])
+    end
+  end
+
+  describe ".kill_port_processes" do
+    it "kills processes on specified ports" do
+      allow(Open3).to receive(:capture2).with("lsof", "-ti", ":3000", err: File::NULL).and_return(["1234", nil])
+      allow(Open3).to receive(:capture2).with("lsof", "-ti", ":3001", err: File::NULL).and_return(["5678", nil])
+      allow(Process).to receive(:pid).and_return(9999)
+
+      expect(Process).to receive(:kill).with("TERM", 1234)
+      expect(Process).to receive(:kill).with("TERM", 5678)
+
+      result = described_class.kill_port_processes([3000, 3001])
+      expect(result).to be true
+    end
+
+    it "returns false when no processes found on ports" do
+      allow(Open3).to receive(:capture2).and_return(["", nil])
+
+      result = described_class.kill_port_processes([3000, 3001])
+      expect(result).to be false
+    end
+  end
+
   describe ".show_help" do
     it "displays help information" do
       expect { described_class.show_help }.to output(%r{Usage: bin/dev \[command\]}).to_stdout_from_any_process