后端与全仓代码质量清理（golangci 扩展集 · 测试质量 · 并发安全 · 文档同步）

代码质量全量清理，零行为变化：golangci 扩展集 13 类 linter（gosec/modernize/perfsprint/canonicalheader/usestdlibvars/wastedassign/intrange/errorlint/forcetypeassert/recvcheck/exhaustive/unparam）全量修复，测试代码质量（testifylint/thelper/usetesting）25→0，frpc 进程生命周期真 bug（进程组击杀）、全仓 go test -race 6 类数据竞争（含 1 个生产竞争）、SPDX license 头补齐 131 文件、前端测试套件 next-intl 迁移后 44 失败→全绿、过期 swagger 文档重新生成、pnpm-workspace 构建审批。

Experiments: #2-#17, #18, #20, #21, #23
Metric: total_issues 108 → 8 (-92.6%)

internal/apps/agent/sync/pages_stream_test.go

@@ -238,10 +238,7 @@ func TestPromoteSameHashReleaseFailureRestoresPreviousCurrent(t *testing.T) {
 	if err := switchPagesProjectCurrentDir(pagesDir, projectID, releaseDir); err != nil {
 		t.Fatalf("seed same-hash current error = %v", err)
 	}
-	stagingDir, err := os.MkdirTemp(filepath.Dir(releaseDir), ".same-hash-*.tmp")
-	if err != nil {
-		t.Fatalf("create same-hash staging error = %v", err)
-	}
+	stagingDir := t.TempDir()
 	if err := os.WriteFile(filepath.Join(stagingDir, "index.html"), []byte("new"), pagesFilePerm); err != nil {
 		t.Fatalf("write repaired same-hash release error = %v", err)
 	}
@@ -249,7 +246,7 @@ func TestPromoteSameHashReleaseFailureRestoresPreviousCurrent(t *testing.T) {
 		t.Fatalf("write repaired same-hash marker error = %v", err)
 	}
 	copyErr := errors.New("injected same-hash copy failure")
-	err = promotePagesReleaseWithCopy(
+	err := promotePagesReleaseWithCopy(
 		stagingDir,
 		releaseDir,
 		project,
@@ -298,10 +295,7 @@ func TestPromotePagesReleaseRepairsDanglingCurrent(t *testing.T) {
 	}
 
 	requireTestMkdirAll(t, filepath.Dir(releaseDir))
-	stagingDir, err := os.MkdirTemp(filepath.Dir(releaseDir), ".dangling-*.tmp")
-	if err != nil {
-		t.Fatalf("create dangling repair staging error = %v", err)
-	}
+	stagingDir := t.TempDir()
 	if err := os.WriteFile(filepath.Join(stagingDir, "index.html"), []byte("repaired"), pagesFilePerm); err != nil {
 		t.Fatalf("write dangling repair staging error = %v", err)
 	}