chore: baseline snapshot before moderation-strictness feature

Repo .git was damaged (refs/ missing, index truncated, object store near-empty).
Repaired via git init (rebuilt refs), stale index preserved as .git/index.corrupt-20260910.bak,
then full worktree committed as a rollback baseline.

internal/shared/multidial_test.go

@@ -0,0 +1,127 @@
+package shared
+
+import (
+	"context"
+	"net"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+)
+
+// startLoopbackListener 在 127.0.0.1 上开一个监听并返回其端口（关闭由 t.Cleanup 托管）。
+func startLoopbackListener(t *testing.T) int {
+	t.Helper()
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+	t.Cleanup(func() { _ = ln.Close() })
+	return ln.Addr().(*net.TCPAddr).Port
+}
+
+func testDialer() *net.Dialer {
+	return &net.Dialer{Timeout: 3 * time.Second, KeepAlive: 30 * time.Second}
+}
+
+// TestDialFirstReachablePicksReachableIP 验证多候选并发拨号会跳过不可达 IP、
+// 选中可达的那个（顺序上不可达在前也不影响结果）。
+func TestDialFirstReachablePicksReachableIP(t *testing.T) {
+	port := startLoopbackListener(t)
+
+	// 127.0.0.2 上没有任何监听 → 该候选必然拨号失败；
+	// 127.0.0.1:port 有监听 → 可达。把坏 IP 放前面，验证不受顺序影响。
+	conn, err := DialFirstReachable(context.Background(), testDialer(), "tcp",
+		[]net.IP{net.ParseIP("127.0.0.2"), net.ParseIP("127.0.0.1")}, strconv.Itoa(port), 6)
+	if err != nil {
+		t.Fatalf("DialFirstReachable returned error: %v", err)
+	}
+	if conn == nil {
+		t.Fatal("DialFirstReachable returned nil conn without error")
+	}
+	// 连接应落在可达的 127.0.0.1 上
+	remote := conn.RemoteAddr().(*net.TCPAddr)
+	if !remote.IP.Equal(net.ParseIP("127.0.0.1")) {
+		t.Fatalf("expected connection to 127.0.0.1, got %s", remote)
+	}
+	_ = conn.Close()
+}
+
+// TestDialFirstReachableAllFail 验证全部候选不可达时返回错误而非死等或空结果。
+func TestDialFirstReachableAllFail(t *testing.T) {
+	// 先开再关，拿到一个确定无监听的端口
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+	closedPort := ln.Addr().(*net.TCPAddr).Port
+	_ = ln.Close()
+
+	start := time.Now()
+	conn, err := DialFirstReachable(context.Background(), testDialer(), "tcp",
+		[]net.IP{net.ParseIP("127.0.0.2"), net.ParseIP("127.0.0.1")}, strconv.Itoa(closedPort), 6)
+	if err == nil {
+		if conn != nil {
+			_ = conn.Close()
+		}
+		t.Fatal("expected error when all candidates unreachable, got nil")
+	}
+	if conn != nil {
+		_ = conn.Close()
+		t.Fatal("expected nil conn on total failure")
+	}
+	if elapsed := time.Since(start); elapsed > 15*time.Second {
+		t.Fatalf("all-fail path took too long: %v", elapsed)
+	}
+}
+
+// TestDialFirstReachableCtxCancel 验证父 context 取消后拨号立即返回（不泄漏、不死锁）。
+func TestDialFirstReachableCtxCancel(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel() // 拨号前已取消
+
+	start := time.Now()
+	conn, err := DialFirstReachable(ctx, testDialer(), "tcp",
+		[]net.IP{net.ParseIP("127.0.0.1")}, "81", 6)
+	if err == nil {
+		if conn != nil {
+			_ = conn.Close()
+		}
+		t.Fatal("expected error after context cancel, got nil")
+	}
+	if conn != nil {
+		_ = conn.Close()
+		t.Fatal("expected nil conn on cancelled context")
+	}
+	if !strings.Contains(err.Error(), "canceled") && !strings.Contains(err.Error(), "deadline") {
+		t.Fatalf("expected context cancellation error, got: %v", err)
+	}
+	if elapsed := time.Since(start); elapsed > 5*time.Second {
+		t.Fatalf("context cancel path took too long: %v", elapsed)
+	}
+}
+
+// TestDialFirstReachableEmptyCandidates 验证空候选返回错误而非 panic。
+func TestDialFirstReachableEmptyCandidates(t *testing.T) {
+	conn, err := DialFirstReachable(context.Background(), testDialer(), "tcp", nil, "80", 6)
+	if err == nil {
+		if conn != nil {
+			_ = conn.Close()
+		}
+		t.Fatal("expected error for empty candidates, got nil")
+	}
+}
+
+// TestDialFirstReachableMaxCandidatesCapped 验证 maxCandidates 截断候选数不会 panic。
+func TestDialFirstReachableMaxCandidatesCapped(t *testing.T) {
+	port := startLoopbackListener(t)
+	conn, err := DialFirstReachable(context.Background(), testDialer(), "tcp",
+		[]net.IP{net.ParseIP("127.0.0.1"), net.ParseIP("127.0.0.1")}, strconv.Itoa(port), 1)
+	if err != nil {
+		t.Fatalf("DialFirstReachable with capped candidates returned error: %v", err)
+	}
+	if conn == nil {
+		t.Fatal("DialFirstReachable returned nil conn without error")
+	}
+	_ = conn.Close()
+}