Fix remaining lint errors missed in previous commit

- fly_replay_test.go: use t.Setenv, remove unused os import
- validation_test.go: fix unchecked tmpFile.Close and os.Remove calls

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: rubys

internal/config/validation_test.go

@@ -215,12 +215,12 @@ applications:
 			if err != nil {
 				t.Fatalf("Failed to create temp file: %v", err)
 			}
-			defer os.Remove(tmpFile.Name())
+			defer func() { _ = os.Remove(tmpFile.Name()) }()
 
 			if _, err := tmpFile.WriteString(tt.config); err != nil {
 				t.Fatalf("Failed to write test config: %v", err)
 			}
-			tmpFile.Close()
+			_ = tmpFile.Close()
 
 			config, err := LoadConfig(tmpFile.Name())
 
@@ -390,12 +390,12 @@ managed_processes: []
 			if err != nil {
 				t.Fatalf("Failed to create temp file: %v", err)
 			}
-			defer os.Remove(tmpFile.Name())
+			defer func() { _ = os.Remove(tmpFile.Name()) }()
 
 			if _, err := tmpFile.WriteString(tt.config); err != nil {
 				t.Fatalf("Failed to write test config: %v", err)
 			}
-			tmpFile.Close()
+			_ = tmpFile.Close()
 
 			config, err := LoadConfig(tmpFile.Name())
 			if err != nil {
@@ -640,12 +640,12 @@ applications:
 			if err != nil {
 				t.Fatalf("Failed to create temp file: %v", err)
 			}
-			defer os.Remove(tmpFile.Name())
+			defer func() { _ = os.Remove(tmpFile.Name()) }()
 
 			if _, err := tmpFile.WriteString(tt.config); err != nil {
 				t.Fatalf("Failed to write test config: %v", err)
 			}
-			tmpFile.Close()
+			_ = tmpFile.Close()
 
 			// Configuration should load without errors even with problematic variable substitution
 			config, err := LoadConfig(tmpFile.Name())
@@ -717,12 +717,12 @@ hooks:
 	if err != nil {
 		b.Fatalf("Failed to create temp file: %v", err)
 	}
-	defer os.Remove(tmpFile.Name())
+	defer func() { _ = os.Remove(tmpFile.Name()) }()
 
 	if _, err := tmpFile.WriteString(testConfig); err != nil {
 		b.Fatalf("Failed to write test config: %v", err)
 	}
-	tmpFile.Close()
+	_ = tmpFile.Close()
 
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {

internal/server/fly_replay_test.go

@@ -3,7 +3,6 @@ package server
 import (
 	"encoding/json"
 	"net/http/httptest"
-	"os"
 	"strings"
 	"testing"
 
@@ -129,8 +128,7 @@ func TestHandleFlyReplay(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			// Set environment variable for current app
 			if tt.currentApp != "" {
-				os.Setenv("FLY_APP_NAME", tt.currentApp)
-				defer os.Unsetenv("FLY_APP_NAME")
+				t.Setenv("FLY_APP_NAME", tt.currentApp)
 			}
 
 			cfg := &config.Config{}
@@ -224,8 +222,7 @@ func TestHandleFlyReplay(t *testing.T) {
 }
 
 func TestHandleFlyReplay_WithAuthorization(t *testing.T) {
-	os.Setenv("FLY_APP_NAME", "myapp")
-	defer os.Unsetenv("FLY_APP_NAME")
+	t.Setenv("FLY_APP_NAME", "myapp")
 
 	cfg := &config.Config{}
 	req := httptest.NewRequest("GET", "/test", nil)