Expandable player: kill sluggish morph (cheaper compositing + snappy spring) — vc=76

- The detail body's alpha fade was rendering the whole scroll subtree to
  an offscreen buffer every frame (CompositingStrategy.Auto goes offscreen
  when alpha<1). Switch to ModulateAlpha — the body's rows don't overlap,
  so the per-draw-op fade is correct and skips the buffer. Main fix.
- Replace the 300ms FastOutSlowIn tween (slow ramp at both ends) with a
  no-bounce StiffnessMedium spring — distance-adaptive, reads as snappy.

buildSrc/src/main/kotlin/ProjectConfig.kt

@@ -9,6 +9,14 @@ const val STRAW_SDK_TARGET = 35
 
 // Sulkta fork — Straw
 //
+// vc=76 / 0.1.0-CJ — expandable-player smoothness pass:
+//   * The detail body no longer renders to an offscreen buffer every
+//     frame during the morph (CompositingStrategy.ModulateAlpha) — that
+//     offscreen alpha pass on the whole scroll subtree was the main
+//     cause of the sluggish feel.
+//   * Morph animation is now a snappy no-bounce spring instead of a
+//     300ms FastOutSlowIn tween (which ramped slowly at both ends).
+//
 // vc=75 / 0.1.0-CI — expandable player (full rearchitect):
 //   * The video page and the bottom minibar are now ONE container that
 //     morphs continuously between them, both directions. Replaces the
@@ -74,6 +82,6 @@ const val STRAW_SDK_TARGET = 35
 // vc=19 / 0.1.0-AE — rust pipeline cutover. Extraction via
 // strawcore-core (Sulkta-Coop/strawcore) via the UniFFI wrapper; no
 // NewPipeExtractor in the runtime path.
-const val STRAW_VERSION_CODE = 75
-const val STRAW_VERSION_NAME = "0.1.0-CI"
+const val STRAW_VERSION_CODE = 76
+const val STRAW_VERSION_NAME = "0.1.0-CJ"
 const val STRAW_APPLICATION_ID = "com.sulkta.straw"

strawApp/src/main/kotlin/com/sulkta/straw/feature/player/ExpandablePlayer.kt

@@ -34,8 +34,8 @@ import android.view.LayoutInflater
 import android.widget.Toast
 import androidx.annotation.OptIn
 import androidx.compose.animation.core.Animatable
-import androidx.compose.animation.core.FastOutSlowInEasing
-import androidx.compose.animation.core.tween
+import androidx.compose.animation.core.Spring
+import androidx.compose.animation.core.spring
 import androidx.compose.foundation.background
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.gestures.Orientation
@@ -82,6 +82,7 @@ import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.CompositingStrategy
 import androidx.compose.ui.graphics.TransformOrigin
 import androidx.compose.ui.graphics.graphicsLayer
 import androidx.compose.ui.platform.LocalContext
@@ -106,8 +107,14 @@ import com.sulkta.straw.feature.detail.VideoDetailViewModel
 import com.sulkta.straw.util.LogDump
 import kotlinx.coroutines.launch
 
-private val ExpandSpec = tween<Float>(durationMillis = 300, easing = FastOutSlowInEasing)
-private val CollapseSpec = tween<Float>(durationMillis = 260, easing = FastOutSlowInEasing)
+// Snappy, no overshoot. A spring adapts its speed to the remaining
+// distance, which reads as more responsive than a fixed-duration tween
+// (the 300ms FastOutSlowIn tween felt sluggish — slow ramp at both ends).
+private val ExpandSpec = spring<Float>(
+    dampingRatio = Spring.DampingRatioNoBouncy,
+    stiffness = Spring.StiffnessMedium,
+)
+private val CollapseSpec = ExpandSpec
 
 /**
  * Hosted in StrawActivity's root Box, above the browse screen. Visible
@@ -269,6 +276,12 @@ fun ExpandablePlayer(
                         val playerBottomNow = lerp(collapsedTopPx, statusTopPx, fr) + expandedHpx * s
                         translationY = playerBottomNow - playerBottomExpandedPx
                         alpha = fr
+                        // ModulateAlpha applies the fade per draw-op instead of
+                        // rendering the whole (heavy) body to an offscreen buffer
+                        // every frame — the body's rows don't overlap, so the
+                        // blend is correct and it's far cheaper. This was the main
+                        // source of the sluggish morph.
+                        compositingStrategy = CompositingStrategy.ModulateAlpha
                     }
                     .background(MaterialTheme.colorScheme.background),
             ) {