feat(bank_panel): docked bank grid with LICE waveform thumbnails (M5 Wave A)

Docked SWELL window toggled by a new action, drawing the current bank as
per-sample min/max thumbnails (PCM_source + peaks) with an in-memory cache.
Pure grid-layout/cache-key math in bank_grid (tested). Renames peaks::Sample
-> AudioSample to avoid colliding with bank_model::Sample.

src/peaks.cpp

@@ -14,7 +14,7 @@
 
 namespace reasampler {
 
-Envelope computeEnvelope(const std::vector<Sample>& interleaved,
+Envelope computeEnvelope(const std::vector<AudioSample>& interleaved,
                          std::size_t channelCount,
                          std::size_t frameCount,
                          std::size_t binCount) {
@@ -48,11 +48,11 @@ Envelope computeEnvelope(const std::vector<Sample>& interleaved,
                 continue; // empty span (binCount > frames) -> keep {0,0}
             }
 
-            const Sample first = interleaved[begin * channelCount + ch];
-            Sample lo = first;
-            Sample hi = first;
+            const AudioSample first = interleaved[begin * channelCount + ch];
+            AudioSample lo = first;
+            AudioSample hi = first;
             for (std::size_t f = begin + 1; f < end; ++f) {
-                const Sample s = interleaved[f * channelCount + ch];
+                const AudioSample s = interleaved[f * channelCount + ch];
                 lo = std::min(lo, s);
                 hi = std::max(hi, s);
             }