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/pluginSupport/OlivePluginInstance.h

@@ -67,7 +67,8 @@ public:
 		: Instance(instance._plugin, *instance._descriptor, instance._context,
 				   instance._interactive)
 	{
-		_clips=instance._clips;
+		// Do NOT shallow-copy _clips: Instance::~Instance() deletes them,
+		// which would cause a double-free. Clips are re-created in populate().
 		_created=instance._created;
 		_clipPrefsDirty=instance._clipPrefsDirty;
 		_continuousSamples=instance._continuousSamples;
@@ -75,7 +76,6 @@ public:
 		_outputPreMultiplication=instance._outputPreMultiplication;
 		_outputFielding=instance._outputFielding;
 		_outputFrameRate=instance._outputFrameRate;
-
 	}
 	explicit OlivePluginInstance(Instance & instance):Instance(instance){};
 	~OlivePluginInstance() override;