test(sidecar): unknown animation state must not read as idle

sidecar/src/test/kotlin/dev/sanderling/sidecar/IdleDetectionTest.kt

@@ -21,11 +21,17 @@ class IdleDetectionTest {
         assertFalse(StubDriverBackend.isAnimationCountIdle("3\n"))
     }
 
-    @Test fun idleWhenOutputEmpty() {
-        assertTrue(StubDriverBackend.isAnimationCountIdle(""))
+    // A dumpsys that said nothing does not say the device is still. Reading
+    // absence as idle is how a settle returns instantly on a degraded link and
+    // hands the runner a screen caught mid-animation; the caller bounds its own
+    // wait, so the cost of being wrong the other way is a wait it already
+    // budgeted for. The exception path of the same probe already answers false.
+    @Test fun unreadableOutputIsNotIdle() {
+        assertFalse(StubDriverBackend.isAnimationCountIdle(""))
+        assertFalse(StubDriverBackend.isAnimationCountIdle("   \n"))
     }
 
-    @Test fun idleWhenOutputIsNotANumber() {
-        assertTrue(StubDriverBackend.isAnimationCountIdle("error: no service"))
+    @Test fun unparseableOutputIsNotIdle() {
+        assertFalse(StubDriverBackend.isAnimationCountIdle("error: no service"))
     }
 }