[fix](trx-frontend): retune center after bw edge drag

Co-authored-by: OpenAI Codex <codex@openai.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-client/trx-frontend/trx-frontend-http/assets/web/app.js

@@ -6905,7 +6905,12 @@ if (spectrumCanvas) {
 
   window.addEventListener("mouseup", async () => {
     if (_bwDragEdge) {
-      try { await postPath(`/set_bandwidth?hz=${Math.round(currentBandwidthHz)}`); } catch (_) {}
+      try {
+        await postPath(`/set_bandwidth?hz=${Math.round(currentBandwidthHz)}`);
+        if (Number.isFinite(lastFreqHz)) {
+          await ensureTunedBandwidthCoverage(lastFreqHz, currentBandwidthHz);
+        }
+      } catch (_) {}
       _bwDragEdge = null;
       _bwDragCanvas = null;
       return;