Inertial touch scrolling for the tracker grid (v0.4.2)

Add fling/drag vertical scrolling to the pattern grid via Modifier.scrollable
(fractional pixel offset for smooth, non-snapping motion). The view still follows
the playhead during playback (and the cursor when stopped) by default; a finger
flick detaches it into free inertial scrolling, and switching to another block
re-attaches the follow (the scroll state is keyed on the active pattern).
Tap-to-focus is unchanged. Patch bump to 0.4.2 (versionCode 9).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/build.gradle.kts

@@ -22,8 +22,8 @@ android {
         // (android.media.midi) and AAudio low-latency audio we rely on.
         minSdk = 26
         targetSdk = 34
-        versionCode = 8
-        versionName = "0.4.1"
+        versionCode = 9
+        versionName = "0.4.2"
 
         // We provide our own instrumentation runner if/when tests are added.
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"