Make the automation release's publish-ordering rule a compile-time guard, not an assert

The assert compiled out under Release's NDEBUG and ran in no test target.
AutomationChannel::release now requires a ReleaseProof that only
publishLiveParams() or noRepublishNeeded() can mint.

src/shell/instrument/processor_state.cpp

@@ -276,16 +276,21 @@ void ReaSamplerProcessor::clearMasterBusClip() {
     meterClip_.store(false, std::memory_order_relaxed);
 }
 
-void ReaSamplerProcessor::publishLiveParams() {
+AutomationChannel::ReleaseProof ReaSamplerProcessor::publishLiveParams() {
     const int rate = builtSampleRate_.load(std::memory_order_relaxed);
-    if (rate <= 0) return;
+    if (rate <= 0) return AutomationChannel::ReleaseProof::noRepublishNeeded();
+    const std::uint32_t before = liveParams_.generation();
     const InstrumentParams params = instrumentParams();
     const instrument::engine::LiveValues block =
         instrument::engine::foldLive(resolvePlay(params.play, rate), params.keyTrack);
-    // livePublishMutex_ enforces the seqlock's single-writer contract (live_params.h) against
-    // reloadInstrument's publish — held for the publish call only, not the fold above.
-    std::lock_guard<std::mutex> lock(livePublishMutex_);
-    liveParams_.publish(block);
+    {
+        // livePublishMutex_ enforces the seqlock's single-writer contract (live_params.h)
+        // against reloadInstrument's publish — held for the publish call only, not the fold
+        // above.
+        std::lock_guard<std::mutex> lock(livePublishMutex_);
+        liveParams_.publish(block);
+    }
+    return AutomationChannel::ReleaseProof::fromPublish(before, liveParams_.generation());
 }
 
 SampleRefs ReaSamplerProcessor::sampleRefs() {