chore: drop the wait_pipe lint exclusion and use gomodguard_v2

Assigning the two pipe halves before returning them removes the gofumpt and
gofmt disagreement that needed a permanent formatter exclusion. gomodguard is
deprecated in golangci-lint v2.12; the v2 linter takes the same configuration.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PvgysXDmhPBBimCReYtA8q
Signed-off-by: Feng Ruohang <rh@vonng.com>

.golangci.yml

@@ -5,7 +5,7 @@ linters:
     - durationcheck
     - forcetypeassert
     - gocritic
-    - gomodguard
+    - gomodguard_v2
     - govet
     - ineffassign
     - misspell
@@ -59,9 +59,6 @@ formatters:
   exclusions:
     generated: lax
     paths:
-      # gofumpt v0.11.0 and Go 1.27's gofmt disagree on the indentation of
-      # multiple composite literals returned from a single statement.
-      - internal/ioutil/wait_pipe\.go$
       - third_party$
       - builtin$
       - examples$

internal/ioutil/wait_pipe.go

@@ -57,11 +57,7 @@ func WaitPipe() (*PipeReader, *PipeWriter) {
 	r, w := io.Pipe()
 	var wg sync.WaitGroup
 	wg.Add(1)
-	return &PipeReader{
+	pr := &PipeReader{PipeReader: r, wait: wg.Wait}
-		PipeReader: r,
+	pw := &PipeWriter{PipeWriter: w, done: wg.Done}
-		wait:       wg.Wait,
+	return pr, pw
-	}, &PipeWriter{
-		PipeWriter: w,
-		done:       wg.Done,
-	}
 }