fix(cw): stop the decoder claiming a healthy signal it cannot hear

With tone shift off and the operator tuned outside 400-1200 Hz, the page did not
go quiet - it went confidently wrong. Three measurements, all reproduced against
the real spectrogram path:

estimatedPitch is (32 + loudestBin) * 12.5 - shiftHz with the bin confined to
0..64, so with no shift applied it can only ever report 400-1200 Hz. It cannot
express 1500 Hz, and it does not try: it publishes whichever window edge the
leakage piles against. For a 1500 Hz tone that is 1200 Hz.

That leakage is not faint. The waterfall normalises to the loudest value on
screen, so 50 of 65 bins clear the 0.06 draw threshold and the picture shows a
keyed-looking column pinned to the right edge - the 1200 Hz column runs 25 times
the 400 Hz one.

signalStrength is prominence over the window mean, so the same leakage scores
0.78 and paints the meter to 78% of full width.

So the operator got a strong-signal bar, a plausible 1200 Hz readout, a picture
that looked like a signal, and an empty transcript, with nothing saying why.

The scan that can see past the window now runs whether or not shifting is
enabled - it is the only measurement that can - and publishes through a new
detectedToneHz flow kept separate from estimatedPitch. Overloading the latter is
what let the 1200 Hz claim out in the first place, so the two meanings stay in
two flows. The shift decision still only happens when the setting is on. Cost is
one 121-bin scan every 2 s.

The meter now reads zero when a tone is out of range and not being shifted in: it
is a claim that something decodable is present, and in that state nothing is.

A line under the waterfall says which case the operator is in - the tone was
moved in, or it is out of range and tone shift is off, naming the frequency and
the remedy. Strings in all nine locales; feature:cw only had five, so values-es,
values-ru, values-si and values-uk are new, with the Turkish apostrophe escaped.

CwToneShifterTest pins the premise the hint rests on: that the scan reports tones
the model window excludes, at 120, 250, 1400 and 1500 Hz.

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

@@ -106,6 +106,9 @@ class CwDeepDecoder(
     private val _estimatedPitch = MutableStateFlow<Float?>(null)
     override val estimatedPitch: StateFlow<Float?> = _estimatedPitch.asStateFlow()
 
+    private val _detectedToneHz = MutableStateFlow<Float?>(null)
+    override val detectedToneHz: StateFlow<Float?> = _detectedToneHz.asStateFlow()
+
     private val _activeShiftHz = MutableStateFlow(0f)
     override val activeShiftHz: StateFlow<Float> = _activeShiftHz.asStateFlow()
 
@@ -324,23 +327,30 @@ class CwDeepDecoder(
             Log.i(TAG, "toneShift: setting changed to $enabled, dropping buffered audio")
             dropBufferedAudio()
             _activeShiftHz.value = 0f
+            _detectedToneHz.value = null
             shiftDecider.reset()
             lastDetectAtMs = 0L
             detectionPool.clear()
             streamingShifter.reset()
         }
 
-        if (!enabled) return resampled
-
+        // Detection runs whether or not shifting is enabled. It is the only measurement
+        // that can see past the model's window, so with it skipped an out-of-window tone
+        // left the UI with nothing truthful to show: the spectrogram's own pitch readout
+        // is arithmetically confined to the window and reports the leakage piled against
+        // the nearest edge, so a 1500 Hz tone published "1200 Hz" and a healthy signal
+        // level while decoding nothing at all.
         detectionPool.add(resampled)
 
         val now = System.currentTimeMillis()
         val elapsed = now - lastDetectAtMs
         if (detectionPool.isReady && elapsed >= DETECT_INTERVAL_MS) {
             lastDetectAtMs = now
-            runDetection(detectionPool.drain())
+            runDetection(detectionPool.drain(), shiftEnabled = enabled)
         }
 
+        if (!enabled) return resampled
+
         // Streaming keeps the Hilbert filter history and mixer phase across chunks;
         // shifting each chunk in isolation distorted the 62 samples at its edges.
         return streamingShifter.process(resampled, _activeShiftHz.value, CwDeepSpectrogram.SAMPLE_RATE)
@@ -365,8 +375,16 @@ class CwDeepDecoder(
      * meant tests could only restate it, and a restated rule cannot fail when the real
      * one is wrong - four injected defects once left the whole suite green.
      */
-    private fun runDetection(sample: FloatArray) {
+    private fun runDetection(sample: FloatArray, shiftEnabled: Boolean) {
         val analysis = CwToneShifter.analyse(sample, CwDeepSpectrogram.SAMPLE_RATE)
+
+        // Published either way: the UI needs the real pitch to say why nothing decodes
+        // when shifting is off and the tone is out of range. Held through silences for
+        // the same reason the shift is - CW is gaps, and a gap is not a retune.
+        analysis.toneHz?.let { _detectedToneHz.value = it.toFloat() }
+
+        if (!shiftEnabled) return
+
         val decision = shiftDecider.accept(analysis)
         _activeShiftHz.value = decision.shiftHz
 
@@ -496,7 +514,16 @@ class CwDeepDecoder(
         _estimatedPitch.value = (absoluteBin * binHz - _activeShiftHz.value).toFloat()
 
         val mean = total / count
-        _signalStrength.value = ((bestValue - mean) / bestValue).coerceIn(0f, 1f)
+        val prominence = ((bestValue - mean) / bestValue).coerceIn(0f, 1f)
+
+        // Zero when the tone is out of range and not being shifted in. The spectrogram
+        // normalises within the window, so a tone outside it still scores well on the
+        // leakage banked up against the nearest edge - measured at 0.78 for a 1500 Hz
+        // tone, a near-full meter next to an empty transcript. The meter is a claim that
+        // something decodable is present, and in that state nothing is.
+        val outOfRange = _activeShiftHz.value == 0f &&
+            _detectedToneHz.value?.let { !CwToneShifter.isInsideWindow(it) } == true
+        _signalStrength.value = if (outOfRange) 0f else prominence
     }
 
     override fun reset() {
@@ -505,6 +532,7 @@ class CwDeepDecoder(
         _historyText.value = ""
         archiveSize = 0
         _estimatedPitch.value = null
+        _detectedToneHz.value = null
         _signalStrength.value = 0f
         _lastInferenceMs.value = 0
         // Re-detect from scratch: the operator may have retuned before resetting.