Reject empty replay files before WebGL loading churn

High-frequency replay switching included a zero-byte sample, which could still enter the browser-to-Unity load path and add avoidable request, parse, status, and GC churn during stress. The bridge now treats an explicitly reported zero-size file as an immediate player-facing failure while leaving normal URL callers without size metadata untouched.

Constraint: Competition package stability favors a narrow Playback-side fix over a replay parser rewrite.
Rejected: Revoke blob object URLs from Unity after terminal load | stress testing showed this can make high-frequency blob loads less stable.
Rejected: Abort and dispose active UnityWebRequest from PreparePlaybackLoad | stress testing showed this can worsen WebGL hangs under rapid blob switching.
Confidence: medium
Scope-risk: narrow
Directive: Do not add aggressive blob revocation or UnityWebRequest disposal on the C# side without rerunning high-frequency WebGL replay stress.
Tested: dotnet format whitespace --folder interface/Unity/Unity-Playback/Assets/Scripts --verify-no-changes
Tested: Unity batchmode WebGL Playback build via WebGLBuildScript.BuildWebGL
Tested: Playback zip extracted and SHA256-compared against interface/Unity/Unity-WebGL/playback, 17/17 files matched
Tested: Three headless Chrome WebGL stress rounds, 80 random rapid loads each across playback (2), playback (1), and playback.thuaipb, no JS exceptions or permanent hang
Not-tested: Full lazy/streaming replay parser redesign for eliminating 3-5 second main-thread parse long tasks

Author: zyfkid

interface/Unity/Unity-Playback/Assets/Scripts/WebGL/WebGLFrameBridge.cs

@@ -74,6 +74,14 @@ public void SetPlaybackFile(string payload)
             if (playbackController == null) { DispatchEvent("playback-error", "missing-playback-controller"); return; }
             uiController?.SetPlaybackPathDisplay(selection.name ?? selection.url);
             DispatchEvent("playback-loading", selection.name ?? selection.url);
+            if (selection.size == 0)
+            {
+                string status = "状态：回放文件为空，请选择有效的 .thuaipb 文件";
+                playbackController.RejectPlaybackLoad(selection.url, selection.name, status);
+                DispatchEvent("playback-error", "file-empty");
+                return;
+            }
+
             if (selection.size > PlaybackController.MaxRemotePlaybackBytes)
             {
                 string status = $"状态：回放文件过大（{selection.size} 字节）";
@@ -228,7 +236,17 @@ private static PlaybackSelection ParsePlaybackSelection(string payload)
             if (string.IsNullOrWhiteSpace(payload)) return null;
             string trimmed = payload.Trim();
             if (!trimmed.StartsWith("{", StringComparison.Ordinal)) return new PlaybackSelection { url = trimmed.Trim('"'), name = trimmed.Trim('"') };
-            try { return JsonUtility.FromJson<PlaybackSelection>(trimmed); } catch { return new PlaybackSelection { url = trimmed }; }
+            try
+            {
+                PlaybackSelection selection = JsonUtility.FromJson<PlaybackSelection>(trimmed);
+                if (trimmed.IndexOf("\"size\"", StringComparison.OrdinalIgnoreCase) < 0)
+                {
+                    selection.size = -1;
+                }
+
+                return selection;
+            }
+            catch { return new PlaybackSelection { url = trimmed }; }
         }
 
         private static PlaybackDataSelection ParsePlaybackDataSelection(string payload)
@@ -264,7 +282,7 @@ private static string NormalizeBase64Payload(string base64)
                 .Replace("\t", string.Empty);
         }
 
-        [Serializable] private class PlaybackSelection { public string url; public string name; public long size; }
+        [Serializable] private class PlaybackSelection { public string url; public string name; public long size = -1; }
         [Serializable] private class PlaybackDataSelection { public string data; public string name; }
         [Serializable]
         private class PlaybackStatus

interface/Unity/Unity-WebGL/Unity-Playback-WebGL.zip

@@ -57,7 +57,7 @@
       }
 
       var thuai9Mode = 'playback';
-      var thuai9BuildStamp = '639152606370429751';
+      var thuai9BuildStamp = '639152674144621830';
       var thuai9Query = new URLSearchParams(window.location.search);
       function thuai9CacheBust(url) {
         return url + (url.indexOf('?') >= 0 ? '&' : '?') + 'v=' + encodeURIComponent(thuai9BuildStamp);