fix: bug-fix sweep across node, audio, render, plugin subsystems

Node core:
- MathNode/TrigonometryNode combo strings realigned with Operation enums
- mathbase scalar/vector operand pick no longer uses bitwise type checks
- NodeSetPositionAndDependenciesRecursively moves dependencies again
- RemoveAllKeyframes undo actually restores keyframes
- NodeGroup GetInputName null-deref guard, passthrough ids use input id
- NodeValueTable::Has is an exact type match; tag fallback only for
  empty tags; kStrCombo/kPushButton get data type names
- delete_all_keyframes no longer loops forever on unparented keyframes;
  keyframe-load failures propagate; rational interpolation falls back to
  double; OpacityEffect no longer leaks its internal MathNode

Audio/footage:
- AudioVisualWaveform: GetSummaryFromTime underflow OOB read, TrimIn
  prepend length bookkeeping, OverwriteSums source channel indexing
- PanNode inserts the pan value into the sample job (keyframed pan
  works); OutputParamsChanged is emitted on device change; PortAudio
  device indices are validated before Pa_GetDeviceInfo
- Footage: AdjustTimeByLoopMode no longer hangs/UBs on degenerate
  lengths, GetStreamIndex bounds-checked, CheckFootage clears stale
  state on missing files, failed probes are not cached,
  FootageDescription::Load requires its own root element

Render/track:
- ViewerOutput pushes the tagged samples value; TrackList disconnects
  the track-height lambda; GetTrackFromReference validity check
- RenderManager dummy backend: null-initialized threads, guarded
  decoder-cache/timer paths; Renderer::Destroy releases color cache
  shaders/textures; unknown dynamic backends no longer alias to oakgl
- SharedMemoryRegion POSIX attach validates segment size; ReadMessage
  skips blank lines instead of failing; GC counter clamped;
  IsRenderingCustomRange implemented; TimeOffsetNode gets a true
  inverse OutputTimeAdjustment; zero-speed clips return the held frame

Plugin/nodes:
- OliveClip: stored default region of definition is honored, on-demand
  images are cached; OliveHost sets host identity properties and logs
  instead of showing modal dialogs offscreen; Plugin.h dead decls gone
- DespillNode guards graph-less use with Rec.709 fallback; description
  typos fixed (despill, swirl); mosaic applies when only one axis
  matches; Windows-only Project filename separator test fixed

app/render/rendermanager.cpp

@@ -220,7 +220,12 @@ RenderTicketPtr RenderManager::RenderFrame(const RenderVideoParams &params)
 	}
 
 	if (worker_params.return_type == ReturnType::kNull) {
-		dry_run_thread_->AddTicket(ticket);
+		if (dry_run_thread_) {
+			dry_run_thread_->AddTicket(ticket);
+		} else {
+			// No render threads (e.g. dummy backend), finish without a result
+			ticket->Finish();
+		}
 	} else if (worker_pool_ &&
 			   worker_pool_->SubmitFrame(ticket, worker_params)) {
 		return ticket;
@@ -247,13 +252,16 @@ RenderTicketPtr RenderManager::RenderAudio(const RenderAudioParams &params)
 	ticket->setProperty("aparam", QVariant::fromValue(params.audio_params));
 	ticket->setProperty("mode", params.mode);
 
-	if (params.generate_waveforms) {
+	if (params.generate_waveforms && !waveform_threads_.empty()) {
 		size_t thread_index = last_waveform_thread_ % waveform_threads_.size();
 		RenderThread *thread = waveform_threads_[thread_index];
 		thread->AddTicket(ticket);
 		last_waveform_thread_++;
-	} else {
+	} else if (audio_thread_) {
 		audio_thread_->AddTicket(ticket);
+	} else {
+		// No render threads (e.g. dummy backend), finish without a result
+		ticket->Finish();
 	}
 
 	return ticket;
@@ -278,6 +286,11 @@ void RenderManager::SetAggressiveGarbageCollection(bool enabled)
 {
 	aggressive_gc_ += enabled ? 1 : -1;
 
+	// Clamp at zero so unbalanced disable calls can't drive the counter negative
+	if (aggressive_gc_ < 0) {
+		aggressive_gc_ = 0;
+	}
+
 	if (aggressive_gc_ > 0) {
 		decoder_clear_timer_->setInterval(kDecoderMaximumInactivityAggressive);
 	} else {
@@ -287,6 +300,11 @@ void RenderManager::SetAggressiveGarbageCollection(bool enabled)
 
 void RenderManager::ClearOldDecoders()
 {
+	if (!decoder_cache_) {
+		// No decoder cache exists on backends without a renderer (e.g. dummy)
+		return;
+	}
+
 	QMutexLocker locker(decoder_cache_->mutex());
 
 	qint64 min_age =