[fix](trx-frontend-http): match waterfall BW resize behavior to waveform

Enable BW edge drag initiation on overview/waterfall canvas and align drag/click suppression behavior with waveform interactions.

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

@@ -6973,6 +6973,10 @@ function handleSpectrumWheel(e, canvasEl) {
 }
 
 function handleSpectrumClick(e, canvasEl) {
+  if (_sDragMoved) {
+    _sDragMoved = false;
+    return;
+  }
   if (!lastSpectrumData || !canvasEl) return;
   const rect = canvasEl.getBoundingClientRect();
   const cssX = e.clientX - rect.left;
@@ -7043,12 +7047,12 @@ function getBwEdgeHit(cssX, cssW, range) {
 // ── Mouse drag to pan / BW resize ─────────────────────────────────────────────
 let _sDragStart = null;  // { clientX, panFrac }
 let _sDragMoved = false;
+let _sDragCanvas = null;
 
-if (spectrumCanvas) {
+function onSpectrumMouseDown(e, canvasEl) {
-  spectrumCanvas.addEventListener("mousedown", (e) => {
+  if (!canvasEl || e.button !== 0) return;
-    if (e.button !== 0) return;
   if (lastSpectrumData) {
-      const rect  = spectrumCanvas.getBoundingClientRect();
+    const rect = canvasEl.getBoundingClientRect();
     const cssX = e.clientX - rect.left;
     const range = spectrumVisibleRange(lastSpectrumData);
     const edge = getBwEdgeHit(cssX, rect.width, range);
@@ -7056,16 +7060,26 @@ if (spectrumCanvas) {
       _bwDragEdge = edge;
       _bwDragStartX = cssX;
       _bwDragStartBwHz = currentBandwidthHz;
-        _bwDragCanvas    = spectrumCanvas;
+      _bwDragCanvas = canvasEl;
       _sDragStart = null;
+      _sDragCanvas = null;
       _sDragMoved = true; // suppress click-to-tune
       return;
     }
   }
   _sDragStart = { clientX: e.clientX, panFrac: spectrumPanFrac };
+  _sDragCanvas = canvasEl;
   _sDragMoved = false;
-  });
+}
 
+if (spectrumCanvas) {
+  spectrumCanvas.addEventListener("mousedown", (e) => { onSpectrumMouseDown(e, spectrumCanvas); });
+}
+if (overviewCanvas) {
+  overviewCanvas.addEventListener("mousedown", (e) => { onSpectrumMouseDown(e, overviewCanvas); });
+}
+
+if (spectrumCanvas || overviewCanvas) {
   window.addEventListener("mousemove", (e) => {
     if (_bwDragEdge && lastSpectrumData) {
       const dragCanvas = _bwDragCanvas || spectrumCanvas;
@@ -7095,7 +7109,9 @@ if (spectrumCanvas) {
       return;
     }
     if (!_sDragStart || !lastSpectrumData) return;
-    const rect  = spectrumCanvas.getBoundingClientRect();
+    const dragCanvas = _sDragCanvas || spectrumCanvas || overviewCanvas;
+    if (!dragCanvas) return;
+    const rect  = dragCanvas.getBoundingClientRect();
     const dx    = e.clientX - _sDragStart.clientX;
     if (Math.abs(dx) > 3) _sDragMoved = true;
     spectrumPanFrac = _sDragStart.panFrac - (dx / rect.width) / spectrumZoom;
@@ -7115,6 +7131,7 @@ if (spectrumCanvas) {
       return;
     }
     _sDragStart = null;
+    _sDragCanvas = null;
   });
 }
 
@@ -7213,7 +7230,6 @@ if (spectrumCanvas) {
 // ── Click to tune (only when not dragging) ────────────────────────────────────
 if (spectrumCanvas) {
   spectrumCanvas.addEventListener("click", (e) => {
-    if (_sDragMoved) { _sDragMoved = false; return; }
     handleSpectrumClick(e, spectrumCanvas);
   });
 }