Port the Min res (minimum auto-resolution) selector into the v3 player (#663)

The v2 control bar exposes a "Min res" selector next to Quality that sets
highway.setMinRenderScale — capping how far the load-adaptive resolution
scaler (feedBack#654) may downscale, or disabling it entirely (Full). The
v3 UI only ported the Quality selector, so v3 users had no way to stop the
highway auto-downscaling to as low as quarter-res on heavy scenes / weak-
GPU launches — pixelated even at Quality = HD, with no workaround (worse
than v2).

Add the Min res row to the v3 viz/quality rail popover, under Quality,
mirroring the v2 control (same options, handler, title, aria). The handler,
the setMinRenderScale/getMinRenderScale API, and the shared app.js init
that syncs the selector's value (guarded by element id) all already exist —
only the v3 markup was missing.

Fixes #662

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

static/v3/index.html

@@ -926,6 +926,15 @@
                         <option value="0.5">Low</option>
                     </select>
                 </div>
+                <div class="v3-pop-row">
+                    <span class="v3-pop-label" id="min-scale-label">Min res</span>
+                    <select id="min-scale-select" onchange="highway.setMinRenderScale && highway.setMinRenderScale(parseFloat(this.value))" class="v3-pop-select" aria-labelledby="min-scale-label" title="Minimum auto resolution — how far the highway may lower its resolution to hold the frame rate on heavy scenes. 'Full' disables auto-downscaling, but the Quality selector still caps the maximum (so it's only full resolution at Quality = HD).">
+                        <option value="0.25">25%</option>
+                        <option value="0.5">50%</option>
+                        <option value="0.75">75%</option>
+                        <option value="1">Full</option>
+                    </select>
+                </div>
                 <div class="v3-pop-row">
                     <span class="v3-pop-label" id="scoreboard-label">Scoreboard</span>
                     <select id="scoreboard-select" onchange="setScoreboard(this.value)" class="v3-pop-select" aria-labelledby="scoreboard-label" title="Highway scoreboard">