fix(cw): stop swallowing coroutine cancellation on pause/resume

用户反馈: 暂停再恢复时经常弹出 "CW decode failed: The coroutine scope
left the composition"。

根因: 暂停 (isListening=false) 使 LaunchedEffect 重启、旧的采集协程被
取消。若此刻 decodeWindow 正在 withContext(Dispatchers.Default) 里做 ONNX
推理, 取消传播时会抛出 LeftCompositionCancellationException
(message 即 "The coroutine scope left the composition", 是 CancellationException
的子类)。processBuffer 的 catch (Throwable) 把它当成解码失败吞掉, 既误报了
错误横幅, 又破坏了协程取消的正常传播。

修复:
- processBuffer 的 decodeWindow catch 里, CancellationException 直接
  rethrow (暂停导致的中断是正常流程, 不是错误)。
- archiveDecode 调用同样包 try-catch, CancellationException rethrow,
  其余异常只记日志不崩溃。

这是协程的标准纪律: 永远不要把 CancellationException 当业务异常吞掉。

版本: 4.5.5 -> 4.5.7 (versionCode 460)。此前多次删 v4.5.5 tag 重打导致
release 页面累积 12 个 draft 草稿, 已全部清除。

core/data/src/main/java/com/rtbishop/look4sat/core/data/cw/CwDeepDecoder.kt

@@ -26,6 +26,7 @@ import com.rtbishop.look4sat.core.domain.cw.CwCtcDecoder
 import com.rtbishop.look4sat.core.domain.cw.CwDeepBuffer
 import com.rtbishop.look4sat.core.domain.cw.CwDeepSpectrogram
 import com.rtbishop.look4sat.core.domain.cw.ICwDecoder
+import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
@@ -185,7 +186,12 @@ class CwDeepDecoder(context: Context) : ICwDecoder {
             if (archiveSize >= ARCHIVE_THRESHOLD) {
                 val audio = archiveBuffer.copyOf(archiveSize)
                 archiveSize = 0
-                archiveDecode(audio)
+                try {
+                    archiveDecode(audio)
+                } catch (t: Throwable) {
+                    if (t is CancellationException) throw t
+                    Log.e(TAG, "archive decode failed", t)
+                }
             }
         }
 
@@ -199,6 +205,11 @@ class CwDeepDecoder(context: Context) : ICwDecoder {
         try {
             decodeWindow(buffer.snapshot())
         } catch (t: Throwable) {
+            // Cancellation is normal when the user pauses: the capture coroutine
+            // is cancelled while an inference is in flight. Never swallow it as
+            // a decode error — rethrow so the coroutine machinery works, and do
+            // not flash a spurious "decode failed" banner.
+            if (t is CancellationException) throw t
             Log.e(TAG, "inference failed", t)
             _errorMessage.value = "CW decode failed: ${t.message ?: t.javaClass.simpleName}"
             runCatching {