fix(dedup): hash WAV fmt+data only, skipping render-varying metadata chunks

hashWavContent walks RIFF chunks and feeds only fmt body + data payload
through FNV-1a ('W' domain-separation prefix), skipping bext/iXML/LIST that
REAPER embeds with per-render origination timestamps. Fallback to whole-file
hashBytes for non-WAV. Wired into both capture commit paths.

Legacy entries keep their stored whole-file hash; a re-capture will not
collapse onto a pre-fix entry -- a one-time clean capture resolves it.

src/capture_realtime.cpp

@@ -512,16 +512,18 @@ CaptureResult finalizeRecording(RealtimeCaptureState& st) {
     result.status  = CaptureStatus::Ok;
     result.sample  = sampleFromRecordedCapture(cap);
 
-    // Content hash: FNV-1a over the (possibly trimmed) bank file bytes so
-    // hashReferencedElsewhere can identify copies in other banks and suppress the
-    // last-reference confirm when another bank still holds the same file.
-    // Best-effort: an unreadable file leaves contentHash empty — the safe,
-    // confirm-eliciting direction (bank_model treats "" as non-participating).
+    // Content hash: WAV-aware FNV-1a over the (possibly trimmed) bank file's fmt+data
+    // chunks so hashReferencedElsewhere can identify copies in other banks and suppress
+    // the last-reference confirm when another bank still holds the same file. Using
+    // hashWavContent (not the raw hashBytes) skips render-varying metadata chunks
+    // (bext origination timestamp, iXML, LIST/INFO, etc.) so two records of identical
+    // audio collapse to the same hash. Best-effort: an unreadable file leaves
+    // contentHash empty — the safe, confirm-eliciting direction (bank_model treats
+    // "" as non-participating).
     {
         const std::vector<std::uint8_t> fileBytes = readAllBytes(destPath);
         if (!fileBytes.empty()) {
-            result.sample.contentHash =
-                hashBytes(fileBytes.data(), fileBytes.size());
+            result.sample.contentHash = hashWavContent(fileBytes);
         }
     }