Fix OFX plugin render failures and stabilize integration tests

This commit resolves several categories of OFX plugin failures that
  manifested as magenta (pink) render output or crashes:

  1. Param default-value initialization
     - IntegerInstance, DoubleInstance, BooleanInstance, ChoiceInstance,
       and StringInstance now read kOfxParamPropDefault from the descriptor
       at construction time. Previously, when no PluginNode was attached
       (integration-test mode), get() returned 0/0.0/false, causing
       generator plugins to receive invalid extent/format/PAR values and
       crash in coordinate assertions.
     - IntegerInstance also fixed uninitialized `id` that caused
       kOfxStatErrBadHandle in CImg plugins.

  2. Clip property initialization
     - newClipInstance() now seeds pixelDepth and components from the
       host VideoParams instead of leaving them as None. This prevents
       Transform3x3Plugin and similar plugins from asserting on
       getPixelComponentCount() during fetchClip inside createInstance.
     - getAspectRatio() and getProjectPixelAspectRatio() now fall back
       to 1.0 when the project's PAR is not yet set, avoiding division-
       by-zero in coordinate conversion.

  3. Frame-rate and time-base preservation
     - setInputTexture() no longer overwrites the clip's frame_rate or
       time_base with the input texture's values. Multi-input plugins
       were crashing because setupClipPreferencesArgs throws when inputs
     have mismatched rates.

  4. Render loop hardening
     - getClipPreferences() is now wrapped in try/catch so that frame-
       rate mismatch exceptions mark render failure instead of aborting
       the render thread.
     - getRegionOfInterestAction() treats kOfxStatErrBadHandle as non-
       fatal and falls back to default RoI.
     - RenderPlugin syncs all clip instances after setVideoParam so that
       getAspectRatio/getFrameRate return valid values before
       createInstanceAction queries them.

  5. Test suite updates
     - All PluginMisc tests now use F32 input to match the host pipeline
       default.
     - CreateGradientTexture fixed to support F32 pixel format.
     - Added CImgBilateral and CImgGuided_MultiInput tests.
     - Secret parameters are now registered as hidden Node inputs so that
       getClipPreferences can read them (fixes generator pink screen).

  6. Debug logging in HostSupport
     - clipGetImage and clipGetRegionOfDefinition now catch exceptions
       and log the failing clip name for easier debugging.

app/node/plugins/Plugin.cpp

@@ -239,9 +239,7 @@ BuildDefaultValues(const std::map<std::string, OFX::Host::Param::Instance *> &pa
 			continue;
 		}
 		const auto &props = param.second->getProperties();
-		if (props.getIntProperty(kOfxParamPropSecret) != 0) {
-			continue;
-		}
+		bool is_secret = props.getIntProperty(kOfxParamPropSecret) != 0;
 		const QString input_id =
 			QString::fromStdString(param.second->getName());
 		if (input_id.isEmpty()) {
@@ -381,9 +379,7 @@ olive::plugin::PluginNode::PluginNode(
 			continue;
 		}
 		const auto &props = param.second->getProperties();
-		if (props.getIntProperty(kOfxParamPropSecret) != 0) {
-			continue;
-		}
+		bool is_secret = props.getIntProperty(kOfxParamPropSecret) != 0;
 		if (type == NodeValue::kNone) {
 			continue;
 		}
@@ -396,6 +392,9 @@ olive::plugin::PluginNode::PluginNode(
 		} else {
 			AddInput(input_id, type);
 		}
+		if (is_secret) {
+			SetInputFlag(input_id, kInputFlagHidden);
+		}
 		const QString label =
 			QString::fromStdString(param.second->getLabel());
 		if (!label.isEmpty()) {