allow scanning all tabs instead of limiting to 4

- Remove the hardcoded 4-tab limit in the find-videos flow
- Add per-tab try/catch so inaccessible tabs are skipped gracefully
- Filter out tabs that produced no frames from the dedup pipeline
- Update button label and status messages accordingly

src/viewer/index.html

@@ -9,7 +9,7 @@
 <body>
   <div id="app">
     <h1>Goon Plugin</h1>
-    <button id="find-btn">Find Videos (4 tabs)</button>
+    <button id="find-btn">Find Videos (all tabs)</button>
     <div id="video-list" class="video-list" style="display:none;"></div>
     <div id="status" class="status" style="min-height:16px;"></div>
     <div id="btn-row" class="btn-row" style="display:none;">