test: cover the popup blacklist UI, tighten audit findings

The delta model was only covered at module level; the popup wiring around
it was not exercised at all. Seven specs now drive the real settings UI in
the packed extension, including the migration path: a pre-v3.1.0 snapshot
is converted on open, the legacy key is removed, and a default missing
from that snapshot is delivered again.

Also from the audit pass:
- await the blacklist read in init instead of firing a floating promise
- unify the debug report on the finder's own candidate list, which the
  separate traversal missed shadow-DOM videos from
- assert that a single candidate is always returned regardless of its
  ranking signals, so no scoring signal can regress a single-player site

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

extension/content.js

@@ -685,16 +685,6 @@
 
                 hcmDeferredSnapBack();             // buffering → wait for ready, then snap once (#3)
 
-            }
-
-            return;
-
-        }
-
-        // Deliberate: offer the choice (Teleparty-style), default = snap back.
-
-        hcmShowDesyncDialog(action, target);
-
             }
 
             return;
@@ -1332,7 +1322,9 @@
             src.connect(dryGain);
             dryGain.connect(outputGain);
             src.connect(compressor);
-            compressor.connect(compGain);
+            compressor.connect(compGain);
+            compGain.connect(outputGain);
+            outputGain.connect(limiter);
             limiter.connect(ctx.destination);
 
             dryGain.gain.value = 1;

extension/popup.js

@@ -392,7 +392,7 @@ async function init() {
     elements.username.value = username;
     syncDevToolsVisibility();
     if (elements.filterNoise) elements.filterNoise.checked = localData.filterNoise !== false;
-    readBlacklistOverrides().then(overrides => renderBlacklistEditor(overrides));
+    renderBlacklistEditor(await readBlacklistOverrides());
     if (elements.autoSyncNextEpisode) elements.autoSyncNextEpisode.checked = localData.autoSyncNextEpisode !== false;
     if (elements.chatEnabled) elements.chatEnabled.checked = localData.chatEnabled === true;
     if (elements.chatNotifications) elements.chatNotifications.checked = localData.chatNotifications !== false;