Detect HW acceleration; default lava off on software renderer; release probe WebGL context

Probes UNMASKED_RENDERER_WEBGL once per page via a throwaway WebGL context; defaults the lava subsystem off on a positive software-renderer match or total WebGL failure; releases the throwaway context via WEBGL_lose_context after reading the renderer string to avoid exhausting the browser's per-page context limit.

DeepDrftTests/WaveformVisualizerControlStateTests.cs

@@ -88,4 +88,93 @@ public class WaveformVisualizerControlStateTests
 
         Assert.That(observedTheaterMode, Is.False);
     }
+
+    // ── ApplyCapabilityDefault: the one-time HW-accel default-set ──
+
+    // No HW accel → lava defaults off, waveform stays on (the whole point of the feature).
+    [Test]
+    public void ApplyCapabilityDefault_NoHardwareAccel_LavaOffWaveformOn()
+    {
+        _state.ApplyCapabilityDefault(hardwareAccelerated: false);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(_state.LavaEnabled, Is.False);
+            Assert.That(_state.WaveformEnabled, Is.True);
+        });
+    }
+
+    // HW accel present → no change; lava keeps its shipped on-default (the common case is untouched).
+    [Test]
+    public void ApplyCapabilityDefault_HardwareAccelerated_LavaStaysOn()
+    {
+        _state.ApplyCapabilityDefault(hardwareAccelerated: true);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(_state.LavaEnabled, Is.True);
+            Assert.That(_state.WaveformEnabled, Is.True);
+        });
+    }
+
+    // No HW accel raises Changed once so the controls UI / bridge / theater observers all react.
+    [Test]
+    public void ApplyCapabilityDefault_NoHardwareAccel_RaisesChanged()
+    {
+        var raised = 0;
+        _state.Changed += () => raised++;
+
+        _state.ApplyCapabilityDefault(hardwareAccelerated: false);
+
+        Assert.That(raised, Is.EqualTo(1));
+    }
+
+    // HW accel present must not churn observers — no Changed when nothing changed.
+    [Test]
+    public void ApplyCapabilityDefault_HardwareAccelerated_DoesNotRaiseChanged()
+    {
+        var raised = 0;
+        _state.Changed += () => raised++;
+
+        _state.ApplyCapabilityDefault(hardwareAccelerated: true);
+
+        Assert.That(raised, Is.Zero);
+    }
+
+    // Guarded to once per session: a second call cannot re-clobber, even with a different verdict.
+    [Test]
+    public void ApplyCapabilityDefault_SecondCall_IsNoOp()
+    {
+        _state.ApplyCapabilityDefault(hardwareAccelerated: true); // first call wins (accelerated → on)
+        _state.ApplyCapabilityDefault(hardwareAccelerated: false); // must be ignored
+
+        Assert.That(_state.LavaEnabled, Is.True);
+    }
+
+    // Must not override an explicit in-session toggle: once applied, a user re-enabling lava on a
+    // software renderer sticks — a later (guarded) call never reverts it.
+    [Test]
+    public void ApplyCapabilityDefault_DoesNotOverrideExplicitUserToggle()
+    {
+        _state.ApplyCapabilityDefault(hardwareAccelerated: false); // default: lava off
+        _state.LavaEnabled = true;                                 // user re-enables at their own risk
+
+        _state.ApplyCapabilityDefault(hardwareAccelerated: false); // guarded → no-op
+
+        Assert.That(_state.LavaEnabled, Is.True);
+    }
+
+    // No HW accel while Theater Mode is on with only lava active → coercion exits theater in the same
+    // cycle (lava off + waveform off would strand theater; here waveform stays on, but verify the
+    // coercion path is exercised when it WOULD strand).
+    [Test]
+    public void ApplyCapabilityDefault_NoHardwareAccel_CoercesStrandedTheater()
+    {
+        _state.WaveformEnabled = false; // only lava active
+        _state.TheaterMode = true;
+
+        _state.ApplyCapabilityDefault(hardwareAccelerated: false); // lava off → both off → strand
+
+        Assert.That(_state.TheaterMode, Is.False);
+    }
 }