Fix setup UX: remove Hz wording and make setup scrollable

app/src/main/java/com/mindmachine/mvp/MainActivity.kt

@@ -20,6 +20,10 @@ import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.safeDrawingPadding
+import androidx.compose.foundation.layout.windowInsetsBottomHeight
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.verticalScroll
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.items
 import androidx.compose.material3.Button
@@ -165,7 +169,7 @@ fun App(vm: MainViewModel = viewModel()) {
                             Column(Modifier.padding(12.dp)) {
                                 Text(p.name, style = MaterialTheme.typography.titleMedium)
                                 Text(p.description)
-                                Text("${p.defaultDurationSec / 60} min • ${p.visualPatternType} • ${p.binauralDifferenceHz} Hz")
+                                Text("${p.defaultDurationSec / 60} min • ${p.visualPatternType} • binaural ${p.binauralDifferenceHz}")
                             }
                         }
                     }
@@ -241,8 +245,16 @@ fun SafetyScreen(onAck: () -> Unit, onHolder: () -> Unit) {
 fun SetupScreen(vm: MainViewModel, onStart: () -> Unit, onHolder: () -> Unit) {
     val ui by vm.ui.collectAsStateWithLifecycle()
     val cfg = ui.config
+    val scrollState = rememberScrollState()
+    val containerModifier = Modifier
+        .fillMaxSize()
+        .background(MaterialTheme.colorScheme.background)
+        .then(if (setupScreenUsesScrollableContainer()) Modifier.verticalScroll(scrollState) else Modifier)
+        .safeDrawingPadding()
+        .padding(horizontal = 16.dp, vertical = 12.dp)
+
     Column(
-        Modifier.fillMaxSize().background(MaterialTheme.colorScheme.background).padding(16.dp),
+        containerModifier,
         verticalArrangement = Arrangement.spacedBy(10.dp)
     ) {
         Text(ui.selectedPreset.name, style = MaterialTheme.typography.headlineSmall, color = MaterialTheme.colorScheme.onBackground)
@@ -259,24 +271,30 @@ fun SetupScreen(vm: MainViewModel, onStart: () -> Unit, onHolder: () -> Unit) {
                 )
             }
         }
-        Text("Flash interval: ${"%.2f".format(flashIntervalMsToSeconds(cfg.flashIntervalMs))} s", color = MaterialTheme.colorScheme.onBackground)
+        Text(setupScreenFlashIntervalLabel(cfg.flashIntervalMs), color = MaterialTheme.colorScheme.onBackground)
         Slider(
             value = flashIntervalMsToSeconds(cfg.flashIntervalMs),
             onValueChange = { vm.setFlashIntervalMs(flashIntervalSecondsToMs(it)) },
             valueRange = 0.05f..2.0f
         )
         Text("Controls how long each frame is shown in the red/green/black pattern.", color = MaterialTheme.colorScheme.onBackground)
-        Text("Carrier ${cfg.carrierFrequencyHz.roundToInt()} Hz", color = MaterialTheme.colorScheme.onBackground)
+        Text("Carrier frequency: ${cfg.carrierFrequencyHz.roundToInt()}", color = MaterialTheme.colorScheme.onBackground)
         Slider(value = cfg.carrierFrequencyHz, onValueChange = vm::setCarrier, valueRange = 80f..400f)
-        Text("Difference ${cfg.binauralDifferenceHz} Hz", color = MaterialTheme.colorScheme.onBackground)
+        Text("Binaural difference: ${cfg.binauralDifferenceHz}", color = MaterialTheme.colorScheme.onBackground)
         Slider(value = cfg.binauralDifferenceHz, onValueChange = vm::setDifference, valueRange = 0.5f..20f)
         Text("Brightness recommendation: keep screen comfortable and avoid eye strain.", color = MaterialTheme.colorScheme.onBackground)
         TextButton(onClick = onHolder) { Text("Holder Guidance") }
         if (ui.error != null) Text(ui.error!!, color = MaterialTheme.colorScheme.error)
         Button(onClick = onStart, modifier = Modifier.fillMaxWidth().height(52.dp)) { Text("Start") }
+        Spacer(Modifier.height(8.dp))
     }
 }
 
+internal fun setupScreenFlashIntervalLabel(flashIntervalMs: Int): String =
+    "Flash interval: ${"%.2f".format(flashIntervalMsToSeconds(flashIntervalMs))} s"
+
+internal fun setupScreenUsesScrollableContainer(): Boolean = true
+
 @Composable
 fun ActiveSessionScreen(vm: MainViewModel, onFinish: () -> Unit, onBackToSetup: () -> Unit) {
     val ui by vm.ui.collectAsStateWithLifecycle()

app/src/main/java/com/mindmachine/mvp/session/SessionValidator.kt

@@ -7,8 +7,8 @@ object SessionValidator {
     fun validate(config: SessionConfig, headsetAvailable: Boolean): String? {
         if (config.durationSec !in 60..(30 * 60)) return "Duration must be 1 to 30 minutes."
         if (config.flashIntervalMs !in 50..2000) return "Flash interval must be 0.05 to 2.00 seconds."
-        if (config.carrierFrequencyHz !in 80f..400f) return "Carrier frequency must be 80 to 400 Hz."
+        if (config.carrierFrequencyHz !in 80f..400f) return "Carrier frequency must be between 80 and 400."
-        if (config.binauralDifferenceHz !in 0.5f..20f) return "Binaural difference must be 0.5 to 20 Hz."
+        if (config.binauralDifferenceHz !in 0.5f..20f) return "Binaural difference must be between 0.5 and 20."
         if (config.mode != SessionMode.VISUAL_ONLY && !headsetAvailable) {
             return "Stereo headphones are required for binaural audio. Connect headphones or switch to Visual-only."
         }

app/src/test/java/com/mindmachine/mvp/SessionValidatorTest.kt

@@ -40,7 +40,7 @@ class SessionValidatorTest {
     fun out_of_range_values_are_blocked() {
         assertEquals("Duration must be 1 to 30 minutes.", SessionValidator.validate(valid.copy(durationSec = 59), true))
         assertEquals("Flash interval must be 0.05 to 2.00 seconds.", SessionValidator.validate(valid.copy(flashIntervalMs = 49), true))
-        assertEquals("Carrier frequency must be 80 to 400 Hz.", SessionValidator.validate(valid.copy(carrierFrequencyHz = 79f), true))
+        assertEquals("Carrier frequency must be between 80 and 400.", SessionValidator.validate(valid.copy(carrierFrequencyHz = 79f), true))
-        assertEquals("Binaural difference must be 0.5 to 20 Hz.", SessionValidator.validate(valid.copy(binauralDifferenceHz = 0.1f), true))
+        assertEquals("Binaural difference must be between 0.5 and 20.", SessionValidator.validate(valid.copy(binauralDifferenceHz = 0.1f), true))
     }
 }

app/src/test/java/com/mindmachine/mvp/SetupScreenUiLogicTest.kt

@@ -0,0 +1,18 @@
+package com.mindmachine.mvp
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class SetupScreenUiLogicTest {
+    @Test
+    fun flash_interval_label_uses_seconds_text_source() {
+        assertEquals("Flash interval: 0.17 s", setupScreenFlashIntervalLabel(167))
+        assertEquals("Flash interval: 2.00 s", setupScreenFlashIntervalLabel(2000))
+    }
+
+    @Test
+    fun setup_screen_layout_uses_scrollable_container() {
+        assertTrue(setupScreenUsesScrollableContainer())
+    }
+}