fix(lotus-audio-inject): close double-publish window on rapid inject actions

playInjectedClip only registered its cleanup (and thus became abortable by a
later clip's replace-mode loop) AFTER publishing. Two inject actions fired in
quick succession could both pass their fetch/decode/publish awaits before
either was registered, so both tracks got published.

Register a synchronous placeholder abort BEFORE the first await: it aborts the
in-flight fetch and flips an `aborted` flag checked after every await, so a
newer clip cancels the older one during the vulnerable window. The real
cleanup replaces the placeholder once the track is live, and if we were
superseded mid-publish we tear the just-published track down immediately.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/lotus/lotusAudioInject.ts

@@ -101,16 +101,42 @@ async function playInjectedClip(
     return;
   }
 
-  // Max ONE clip at a time (replace mode): stop any in-flight clip before
-  // starting a new one, so clips can't overlap or be spammed. Runs
-  // synchronously before the first await, and each cleanup() is idempotent and
-  // removes itself from activeClips (so no track leak). The host also debounces
-  // the button; together they cover the brief fetch window.
+  // Max ONE clip at a time (replace mode): stop any in-flight or playing clip
+  // before starting a new one, so clips can't overlap or be spammed.
   for (const abort of [...activeClips]) abort();
 
-  const resp = await fetch(url, { credentials: "omit", mode: "cors" });
+  // A second inject action can arrive while THIS one is still awaiting its
+  // fetch/decode/publish — before its real cleanup() exists. Register a
+  // synchronous placeholder abort NOW, BEFORE the first await, so the
+  // replace-mode loop above (run by that later action) cancels this one;
+  // otherwise both clips would sail past their awaits and DOUBLE-PUBLISH. The
+  // placeholder aborts the in-flight fetch and flips `aborted`, which we check
+  // after every await; the real cleanup() replaces it once the track is live.
+  let aborted = false;
+  const controller = new AbortController();
+  const placeholder = (): void => {
+    aborted = true;
+    controller.abort();
+    activeClips.delete(placeholder);
+  };
+  activeClips.add(placeholder);
+
+  let resp: Response;
+  try {
+    resp = await fetch(url, {
+      credentials: "omit",
+      mode: "cors",
+      signal: controller.signal,
+    });
+  } catch (e) {
+    // Superseded by a newer clip mid-fetch — expected, not a failure.
+    if (aborted) return;
+    throw e;
+  }
+  if (aborted) return;
   if (!resp.ok) throw new Error(`fetch ${url} -> ${resp.status}`);
   const arrayBuffer = await resp.arrayBuffer();
+  if (aborted) return;
 
   const ctx = new AudioContext();
   // The action arrives via host postMessage, not a gesture in this iframe, so
@@ -121,6 +147,10 @@ async function playInjectedClip(
   } catch {
     /* best effort */
   }
+  if (aborted) {
+    void ctx.close();
+    return;
+  }
   if (ctx.state !== "running")
     logger.warn(`[lotus] inject_audio: AudioContext is ${ctx.state}`);
 
@@ -131,6 +161,10 @@ async function playInjectedClip(
     void ctx.close();
     throw e;
   }
+  if (aborted) {
+    void ctx.close();
+    return;
+  }
 
   const dest = ctx.createMediaStreamDestination();
   const gain = ctx.createGain();
@@ -183,8 +217,20 @@ async function playInjectedClip(
     }
     void ctx.close().catch(() => undefined);
   };
+  // Swap the synchronous placeholder for the real cleanup: from here an abort
+  // (teardown or a newer clip) must unpublish the LIVE track, not just cancel a
+  // fetch. This delete+add is synchronous (no await), so a newer clip's
+  // replace-mode loop always sees exactly one of {placeholder, cleanup}.
+  activeClips.delete(placeholder);
   activeClips.add(cleanup);
 
+  // If a newer clip aborted us WHILE we were publishing, tear down now so we
+  // don't leave an orphan track published after it ran its replace-mode loop.
+  if (aborted) {
+    cleanup();
+    return;
+  }
+
   source.onended = cleanup;
   // Safety net: clip metadata can lie (NaN/huge duration), so force teardown
   // after a sane, capped delay.