fix(cw): the record deleted its own text while decoding

The record pane concatenated the live decode onto the archived text. The live decode
is the 20 s window, replaced wholesale every 1.5 s because DeepCW is a whole-segment
CTC model that rewrites earlier characters as more context arrives. So the tail of
the record kept changing and could get shorter - text vanishing from under the
operator while the decoder was still running.

A previous attempt (828fd0fb) added decodePending() to cover the gap while audio
waits to be archived, but the call site was never wired up. The function had no
callers and pendingText was only ever cleared, never assigned, so that fix has never
once run and the gap it targeted stayed open. Both are deleted here.

The record now binds to archived text only, which is append-only, so it cannot
shrink. That moves the whole problem to latency, which was 20 s window + 15 s batch:
nothing at all in the record for the first 35 s of a session, and thereafter a stall
of up to 15 s each cycle. The batch is now 4 s, holding the stall under the ~4.7 s a
seven-character call sign takes at 18 WPM, while the archive path still fires less
than half as often as the live redecode.

Neither holding place drains on its own: the live window only reaches the archive by
being pushed out by newer audio, and the pending batch only by filling up. So pausing
or leaving the screen discarded whatever was in flight - the end of every
transmission, the part with the call sign in it. flush() archives both, pending batch
first so the text is not transposed, and is called on pause and before close(). On
the way out it runs on appScope, because the screen's own scope is cancelled as it
leaves and would abort the decode.

Also: the record was an unlabelled grey box showing a bare ellipsis, which reads as a
disabled text field. It now has a label, an empty state that says what it is for, and
a copy button - until now there was no way to get the decoded text off the screen at
all, so an operator who had just copied a call sign by ear had to transcribe it a
second time by hand.

CwArchiveTimingTest covers the timing against the real constants rather than copies;
it caught a 5 s batch exceeding the call-sign bound during this change. The archive
path had no test coverage before.

feature/cw/src/main/java/com/rtbishop/look4sat/feature/cw/CwDecodeScreen.kt

@@ -58,9 +58,11 @@ import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
+import androidx.compose.ui.platform.LocalClipboardManager
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.text.AnnotatedString
 import androidx.compose.ui.text.font.FontFamily
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.unit.dp
@@ -108,6 +110,12 @@ fun CwDecodeScreen() {
     // Hoisted so the toolbar button can reach it: the record below does not follow
     // the decode, so jumping to the newest text has to be an explicit action.
     val transcriptScroll = rememberScrollState()
+    val clipboard = LocalClipboardManager.current
+    val showToast = remember { container.provideShowToast() }
+    val copiedMessage = stringResource(R.string.cw_copied)
+    val emptyRecordMessage = stringResource(R.string.cw_record_empty)
+    // Archiving the tail on the way out has to outlive this composable's own scope.
+    val appScope = container.appScope
 
     val decodedText by decoder.decodedText.collectAsState()
     val historyText by decoder.historyText.collectAsState()
@@ -130,7 +138,13 @@ fun CwDecodeScreen() {
     // permission so granting the permission mid-flow restarts collection
     // (isListening may already be true when the launcher returns).
     LaunchedEffect(isListening, permissionGranted) {
-        if (!isListening) return@LaunchedEffect
+        if (!isListening) {
+            // Pausing must not throw away the tail. The live window plus the batch waiting to
+            // be archived are both still holding audio at this point, and nothing else ever
+            // decodes either of them, so the end of the transmission would be lost outright.
+            decoder.flush()
+            return@LaunchedEffect
+        }
         if (!permissionGranted) {
             permissionLauncher.launch(Manifest.permission.RECORD_AUDIO)
             return@LaunchedEffect
@@ -143,8 +157,14 @@ fun CwDecodeScreen() {
 
     DisposableEffect(Unit) {
         onDispose {
-            // OrtSession holds native memory and must be released explicitly.
-            decoder.close()
+            // Archive the tail before tearing down, on a scope that outlives this composable:
+            // the screen's own scope is cancelled as it leaves, which would abort the decode.
+            // close() waits for it, because the inference needs the session it is closing.
+            appScope.launch {
+                runCatching { decoder.flush() }
+                // OrtSession holds native memory and must be released explicitly.
+                decoder.close()
+            }
         }
     }
 
@@ -162,6 +182,24 @@ fun CwDecodeScreen() {
                     .weight(1f)
                     .padding(start = 12.dp)
             )
+            // Copy the record out. The decoder is built fresh every time this screen is opened,
+            // so leaving the screen loses the transcript - and until now there was no way at all
+            // to get the text off it. An operator who has just copied a callsign by ear should not
+            // have to transcribe it a second time by hand.
+            IconButton(
+                onClick = {
+                    if (historyText.isNotEmpty()) {
+                        clipboard.setText(AnnotatedString(historyText))
+                        showToast(copiedMessage)
+                    }
+                },
+                enabled = historyText.isNotEmpty()
+            ) {
+                Icon(
+                    painter = painterResource(CoreR.drawable.ic_save),
+                    contentDescription = stringResource(R.string.cw_copy)
+                )
+            }
             // Jump to the newest text. The record below deliberately does not follow the decode,
             // so this is how you get back to the bottom after reading earlier traffic.
             IconButton(onClick = { scope.launch { transcriptScroll.animateScrollTo(transcriptScroll.maxValue) } }) {
@@ -239,6 +277,16 @@ fun CwDecodeScreen() {
                 .padding(horizontal = 12.dp, vertical = 6.dp)
         )
 
+        // The pane below was an unlabelled grey box showing a bare ellipsis, which reads as a
+        // disabled text field rather than a transcript. Naming it is what makes the split
+        // between the live line above and the record below legible at all.
+        Text(
+            text = stringResource(R.string.cw_record_label),
+            style = MaterialTheme.typography.labelMedium,
+            color = MaterialTheme.colorScheme.onSurfaceVariant,
+            modifier = Modifier.padding(start = 12.dp, top = 4.dp)
+        )
+
         Box(
             modifier = Modifier
                 .weight(1f)
@@ -247,7 +295,13 @@ fun CwDecodeScreen() {
                 .clip(RoundedCornerShape(8.dp))
                 .background(MaterialTheme.colorScheme.surfaceVariant.copy(alpha = 0.4f))
         ) {
-            val transcript = (historyText + decodedText).ifEmpty { "…" }
+            // The record shows settled text only. decodedText is the live 20-second window,
+            // which the model rewrites from scratch every 1.5 seconds as more context arrives -
+            // right for the line above, where the newest guess is what you want, but it meant the
+            // bottom of the record kept changing and sometimes got shorter. That reads as the
+            // decoder deleting what it just wrote, which for something whose whole purpose is to
+            // be read back is the one thing it must not do.
+            val transcript = historyText.ifEmpty { emptyRecordMessage }
             // This pane does not follow the decode. The single line above it is where new
             // characters appear; this is the record, and a record that scrolls itself is worse
             // than paper - you cannot read back over what just arrived because it keeps moving.

feature/cw/src/main/res/values-zh/app_values.xml

@@ -14,4 +14,8 @@
     <string name="cw_waterfall_shifted">音调 %1$d 赫兹，已搬入解码范围</string>
     <string name="cw_waterfall_outside">音调 %1$d 赫兹，在解码范围外</string>
     <string name="cw_waterfall_inside">音调 %1$d 赫兹</string>
+    <string name="cw_copy">复制记录</string>
+    <string name="cw_copied">记录已复制</string>
+    <string name="cw_record_label">记录</string>
+    <string name="cw_record_empty">解码文字会汇集到这里。离开本页前请复制：记录不会被存下来。</string>
 </resources>

feature/cw/src/main/res/values/app_values.xml

@@ -14,4 +14,8 @@
     <string name="cw_waterfall_shifted">tone at %1$d hertz, moved into the decoder range</string>
     <string name="cw_waterfall_outside">tone at %1$d hertz, outside the decoder range</string>
     <string name="cw_waterfall_inside">tone at %1$d hertz</string>
+    <string name="cw_copy">Copy the record</string>
+    <string name="cw_copied">Record copied</string>
+    <string name="cw_record_label">Record</string>
+    <string name="cw_record_empty">Decoded text collects here. Copy it before leaving this screen: the record is not stored.</string>
 </resources>