[feat](trx-frontend-http): centre the radio controls, split off the mode row

The controls every rig has — mode, wheel, tune step, transmit — now sit
as a centred block rather than packed against the left edge.

What the current mode adds moves out from among them: WFM's six controls
stretched the row sideways whenever it was active, pushing the wheel and
the step pickers off centre, and SAM did the same on a smaller scale.
They get a row of their own below a divider, which appears and leaves
with them — an empty one would still take a track and a gap in the tray
and draw its divider under controls it has nothing to do with.

Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-client/trx-frontend/trx-frontend-http/assets/web/index.html

@@ -256,6 +256,16 @@ SPDX-License-Identifier: GPL-2.0-or-later
                   </div>
                 </div>
               </div>
+              <div class="controls-col controls-col-power label-below-col" id="tx-power-col">
+                <div class="label"><span>Transmit / Power</span></div>
+                <div class="btn-grid">
+                  <button id="ptt-btn" type="button" aria-pressed="false">Start TX</button>
+                  <button id="power-btn" type="button" aria-pressed="false">Power On</button>
+                  <button id="lock-btn" type="button" aria-pressed="false">Lock Tuning</button>
+                </div>
+              </div>
+            </div>
+            <div class="controls-row controls-row-mode full-row" id="mode-controls-row" style="display:none">
               <div class="controls-col controls-col-wfm label-below-col" id="wfm-controls-col" style="display:none;">
                 <div class="inline wfm-controls-inline">
                   <label class="wfm-control">
@@ -313,14 +323,6 @@ SPDX-License-Identifier: GPL-2.0-or-later
                 </div>
                 <div class="label"><span>SAM</span></div>
               </div>
-              <div class="controls-col controls-col-power label-below-col" id="tx-power-col">
-                <div class="label"><span>Transmit / Power</span></div>
-                <div class="btn-grid">
-                  <button id="ptt-btn" type="button" aria-pressed="false">Start TX</button>
-                  <button id="power-btn" type="button" aria-pressed="false">Power On</button>
-                  <button id="lock-btn" type="button" aria-pressed="false">Lock Tuning</button>
-                </div>
-              </div>
             </div>
             <div class="full-row label-below-row" id="vfo-row">
               <div class="label"><span>VFO</span></div>