fix(macos): rewrite player state to mirror Windows frame pipeline

Replace the timer-driven frame/position loops with a producer/consumer
coroutine pipeline backed by a drop-oldest channel, content-hash dedup,
and triple-buffered Skia bitmaps to fix tearing and stalls. Drive the
timeline from a dedicated AVPlayer clock poll since AVFoundation reuses
CVPixelBuffers and frame-derived position freezes on low-motion content.
Honor row padding in calculateFrameHash so true pixels are sampled, and
correct display aspect ratio for anamorphic content.

Author: Buffersolve

mediaplayer/src/jvmMain/kotlin/io/github/kdroidfilter/composemediaplayer/mac/MacFrameUtils.kt

@@ -4,14 +4,23 @@ import java.nio.ByteBuffer
 
 internal fun calculateFrameHash(
     buffer: ByteBuffer,
-    pixelCount: Int,
+    width: Int,
+    height: Int,
+    rowBytes: Int,
 ): Int {
-    if (pixelCount <= 0) return 0
+    if (width <= 0 || height <= 0) return 0
 
+    val pixelCount = width * height
     var hash = 1
     val step = if (pixelCount <= 200) 1 else pixelCount / 200
-    for (i in 0 until pixelCount step step) {
-        hash = 31 * hash + buffer.getInt(i * 4)
+    var i = 0
+    while (i < pixelCount) {
+        // Map the linear sample index to its real byte offset, honoring row padding
+        // (rowBytes may exceed width*4) so we sample true pixels rather than padding bytes.
+        val x = i % width
+        val y = i / width
+        hash = 31 * hash + buffer.getInt(y * rowBytes + x * 4)
+        i += step
     }
     return hash
 }