Expand Google Test coverage across core subsystems

Add and extend unit tests for:
- Task manager (failed tasks, progress signals, multiple tasks)
- Undo stack (multiple undo/redo, push-after-undo, clear, multi-command)
- Config defaults and graphics backend string conversion
- Node keyframe serialization and default state
- Node value string round-trips and table operations
- Node globals and project settings/serialization
- Timeline coordinate, workarea, and marker commands
- Color LUT processor and OCIO transform handling
- Common utilities (range, file functions, Qt helpers, XML utils)
- Render enums (loop mode, alpha association)
- Shader resource availability
- Module smoke tests for Tool and HumanStrings

All tests pass including RenderWorkerFootage GPU worker tests after
rebuilding the stale olive-render-worker binary.

tests/gtest/render_loopmode_test.cpp

@@ -0,0 +1,10 @@
+#include <gtest/gtest.h>
+
+#include "render/loopmode.h"
+
+TEST(LoopMode, ValuesAreDistinct)
+{
+	EXPECT_NE(olive::LoopMode::kLoopModeOff, olive::LoopMode::kLoopModeLoop);
+	EXPECT_NE(olive::LoopMode::kLoopModeOff, olive::LoopMode::kLoopModeClamp);
+	EXPECT_NE(olive::LoopMode::kLoopModeLoop, olive::LoopMode::kLoopModeClamp);
+}