revert(extension): drop post-3.1.2 frame-targeting band-aids

Restores extension/ to the state directly after webNavigation was removed
(4d78970). The six follow-up commits layered heuristics on an unverified
premise (frame-ID sweeps, multi-phase probes, retry loops) without fixing
the underlying resolver. They are removed so the real fix can be built on
a known state.

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

extension/content.js

@@ -867,30 +867,19 @@
         if (wasDesynced) {
 
             runtimeMessage({ type: 'HCM_DESYNC_STATE', desynced: false }).catch(() => {});
-        }
-
-        // Resync to the host's current position (retries if host state not yet known).
-
-        hcmRequestHostSyncWithRetry();
-
-        reportLog('Host-only: resynced with the host', 'info');
-
-    }
-
-
-
+        }
+
+        // Resync to the host's current position (retries if host state not yet known).
+
+        hcmRequestHostSyncWithRetry();
+
+        reportLog('Host-only: resynced with the host', 'info');
+
     }
-
-        if (hcmBadgeHost) return;
-
-        if (!document.body) {
-
-            // Body not ready yet (very early injection). Defer until DOMReady,
-
-            // otherwise the desynced user silently never sees the badge (L-4).
-
-            if (!hcmBadgePending) {
-
+
+
+
+    function hcmShowBadge() {
 
         if (hcmBadgeHost) return;
 
@@ -918,9 +907,8 @@
                 }
 
             }
-        b.append(hcmEl('span', null, '● ' + hcmStrings.badge), hcmEl('span', 'text-decoration:underline', hcmStrings.resync));
-
-        b.addEventListener('click', hcmExitDesync);
+
+            return;
 
         }
 
@@ -1250,7 +1238,7 @@
 
         let bestRank = null;
 
-
+        for (const video of candidates) {
 
             if (!video || video.tagName !== 'VIDEO' || !isVideoRendered(video)) continue;
             const rank = VIDEO_RANKING_SIGNALS.map(signal => signal(video));
@@ -2074,7 +2062,7 @@
 
             // host commands. Only ACK FORCE_SYNC_PREPARE — that's the one the host's
 
-                        runtimeMessage({ type: 'FORCE_SYNC_ACK' }).catch(() => {});
+            // force-sync flow actually waits on. Skipping CMD_ACKs for PLAY/PAUSE/SEEK
 
             // is intentional so the host's UI honestly reflects that we didn't apply
 
@@ -2129,7 +2117,7 @@
                     return;
 
                 }
-                tryMediaAction(EVENTS.PAUSE);
+
             }