Add lcameraBuff Stage 2 plugin with YUV attach and unit tests.

Introduce params parsing, pixel/format decisions, capture layout, shared
YuvStimProducer per camera, and channel stimulus buffers with attach flow.

Co-authored-by: Cursor <cursoragent@cursor.com>

stimBuffApis/lcameraBuff/pixelAndColorFormatDecisions.h

@@ -0,0 +1,59 @@
+#ifndef LCAMERA_BUFF_PIXEL_AND_COLOR_FORMAT_DECISIONS_H
+#define LCAMERA_BUFF_PIXEL_AND_COLOR_FORMAT_DECISIONS_H
+
+#include <cameraModeRequest.h>
+#include <cstddef>
+
+/**
+ * Y/U/V channel sizing for lcameraBuff.
+ *
+ * lcameraBuff exports three quale ifaces (colour-yuv-y/u/v), each backed by a
+ * separate deinterleaved channel buffer. libcamera, however, negotiates a single
+ * configured pixel format (YUYV, NV12, YUV420, etc.) that may be packed or
+ * multi-plane. This module bridges that gap at attach time: it classifies the
+ * configured fourcc into a chroma subsampling family (420 / 422 / 444) and
+ * computes how many bytes each deinterleaved Y, U, or V plane needs for the
+ * negotiated width and height.
+ *
+ * What it provides to the stimbuff:
+ * - YuvChromaSubsampling on YuvStimProducer (derived from configured mode)
+ * - channelByteSize for each YuvChannelStimulusBuffer / StagingBuffer mmap
+ *
+ * Capture layout (packed vs planar, direct vs deinterleaved backing) is handled
+ * separately by yuvCaptureLayout.h; this module is only plane geometry and
+ * byte counts. Future capture/deinterleave stages must write into buffers sized
+ * by these functions.
+ */
+
+namespace smo {
+namespace stim_buff {
+namespace lcamera_buff {
+
+enum class YuvChannelKind
+{
+	Y,
+	U,
+	V,
+};
+
+enum class YuvChromaSubsampling
+{
+	Yuv420,
+	Yuv422,
+	Yuv444,
+};
+
+YuvChromaSubsampling classifyYuvChromaSubsampling(
+	const lcamera_dev::LcameraDevConfiguredCameraMode& configuredMode);
+
+size_t computeDeinterleavedChannelByteSize(
+	YuvChannelKind channel,
+	unsigned width,
+	unsigned height,
+	YuvChromaSubsampling subsampling);
+
+} // namespace lcamera_buff
+} // namespace stim_buff
+} // namespace smo
+
+#endif // LCAMERA_BUFF_PIXEL_AND_COLOR_FORMAT_DECISIONS_H