🐛 fix(update): 修复 Win10 自动更新时文件被占用导致替换失败

- 冷却期：进程退出后增加 3 秒等待，确保 Win10 内核释放 exe 文件句柄
- 替换策略：新增 rename-before-replace 机制，先重命名旧文件再复制新文件
- 退避重试：替换固定 1 秒间隔为指数退避（1s→2s→3s→5s），总等待约 36 秒
- 残留清理：替换成功后删除 .old 残留文件
- 测试覆盖：新增 TestBuildWindowsScriptWin10Fixes 验证全部修复点

internal/app/methods_update_windows_script_test.go

@@ -38,3 +38,37 @@ func TestBuildWindowsScriptKeepsBatchForSyntax(t *testing.T) {
 		}
 	}
 }
+
+func TestBuildWindowsScriptWin10Fixes(t *testing.T) {
+	script := buildWindowsScript(
+		`C:\tmp\GoNavi-v0.5.0-windows-amd64.exe`,
+		`C:\Program Files\GoNavi\GoNavi.exe`,
+		`C:\Program Files\GoNavi\.gonavi-update-windows-v0.5.0`,
+		`C:\Program Files\GoNavi\logs\update-install.log`,
+		99999,
+	)
+
+	// 验证 Win10 关键修复点
+	win10Fixes := []struct {
+		desc  string
+		token string
+	}{
+		{"cooldown after process exit", `timeout /t 3 /nobreak >nul`},
+		{"cooldown log", `call :log cooldown finished, starting file replace`},
+		{"rename-before-replace strategy", `ren "%TARGET%" "%TARGET_NAME%.old"`},
+		{"copy after rename", `copy /Y "%SOURCE_EXE%" "%TARGET%"`},
+		{"restore on copy failure", `ren "%TARGET_NAME%.old" "%TARGET_NAME%"`},
+		{"direct move fallback", `call :log rename strategy failed, trying direct move`},
+		{"exponential backoff tier 1", `if !RETRY! GEQ 3 set /a WAIT=2`},
+		{"exponential backoff tier 2", `if !RETRY! GEQ 6 set /a WAIT=3`},
+		{"exponential backoff tier 3", `if !RETRY! GEQ 9 set /a WAIT=5`},
+		{"retry limit 15", `if !RETRY! LSS 15`},
+		{"cleanup old file", `del /F /Q "%TARGET%.old"`},
+	}
+	for _, fix := range win10Fixes {
+		if !strings.Contains(script, fix.token) {
+			t.Errorf("Win10 fix missing [%s]: expected token: %s", fix.desc, fix.token)
+		}
+	}
+}
+