iter39 α-31: H264 Hi10P + HEVC Main10 sub-profile support (10-bit, rkvdec NV15)

Adds VAProfileH264High10 and VAProfileHEVCMain10 to the libva-v4l2-request
backend. RK3399 rkvdec emits decoded frames as V4L2_PIX_FMT_NV15 (4 × 10-bit
values packed in 5 bytes per element); VAAPI consumers receive standard
VA_FOURCC_P010 via a new userspace unpack in copy_surface_to_image.

VP9 Profile 2 explicitly NOT added — RK3399 rkvdec kernel ctrl table
caps at V4L2_MPEG_VIDEO_VP9_PROFILE_0 (rkvdec.c::rkvdec_vp9_ctrl_descs).

Touchpoints (per Phase 5 sonnet-architect review amendments):
  - include/drm_fourcc.h: define DRM_FORMAT_NV15 (vendored libdrm lacks it)
  - src/nv15.{c,h}: NV15 → P010 plane unpack (LSB-first, per
    Documentation/userspace-api/media/v4l/pixfmt-nv15.rst)
  - src/video.c: NV15 entry in formats[] (else NULL-deref on video_format_find)
  - src/codec.c: pixelformat_for_profile cases for Hi10P + Main10
  - src/config.c: enumeration, validation, entrypoints, RT_FORMAT_YUV420_10
    advertisement for 10-bit profiles
  - src/context.c: per-profile CAPTURE pix_fmt (NV12/NV15), 10-bit synthetic
    SPS (bit_depth_luma_minus8=2), video_format invalidation on bit-depth
    transition (sibling to iter38 device-switch invalidation), is_10bit flag
  - src/surface.c: RT_FORMAT_YUV420_10 admission, NV15 fourcc on PRIME export
  - src/image.c: P010 reporting in DeriveImage + QueryImageFormats,
    P010-aware sizing in CreateImage, NV15 → P010 unpack call in
    copy_surface_to_image (gated on is_10bit + image.format.fourcc == P010)
  - src/picture.c: 4 switch blocks route Hi10P/Main10 to existing H264/HEVC
    per-codec paths
  - src/request.h: MAX_PROFILES bump 11 → 13, driver_data->is_10bit flag

Scope: COPY path (vaGetImage / vaDeriveImage) only. Standard ffmpeg-vaapi
hwdownload, mpv vaapi-copy, and any consumer using vaGetImage works
end-to-end. PRIME-path consumers that only know NV12/P010 must use the
COPY path; PRIME consumers aware of NV15 (panfrost-Mesa et al.) get the
correct fourcc on RequestExportSurfaceHandle. PRIME-side P010 emission is
follow-up scope (would need DRM_FORMAT_P010 + per-plane unpack into a
GPU-accessible buffer).

Compile-tested on boltzmann (aarch64 native, gcc 15.2.1, libva 1.23.0,
libdrm 2.4.133): clean build, .so produced, 0 new warnings.

Phase 0/2 evidence: linux-mmind-v7.0 drivers/media/platform/rockchip/rkvdec.
rkvdec_h264_decoded_fmts[] and rkvdec_hevc_decoded_fmts[] both list NV15;
ctrl tables cap at HEVC MAIN_10 and H264 HIGH_422_INTRA (Hi10P < cap, not
in menu_skip_mask). image_fmt resolution (rkvdec-h264-common.c:196,
rkvdec-hevc-common.c:467) dispatches on bit_depth_luma_minus8 only.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/nv15.h

@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2026 claude-noether <claude-noether@reauktion.de>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
+ * IN NO EVENT SHALL PRECISION INSIGHT AND/OR ITS SUPPLIERS BE LIABLE FOR
+ * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef _NV15_H_
+#define _NV15_H_
+
+#include <stdint.h>
+
+/*
+ * Unpack one plane of V4L2_PIX_FMT_NV15 (4 × 10-bit values packed into
+ * 5 consecutive bytes, LSB-first) into VA_FOURCC_P010 (16-bit per pixel,
+ * value in bits [15:6], zeros in [5:0]).
+ *
+ * Layout per Documentation/userspace-api/media/v4l/pixfmt-nv15.rst.
+ * Call once per plane: luma (W × H, src_stride = ceil(W/4)*5) and chroma
+ * (W × H/2 — same width because UV are interleaved 10-bit values).
+ *
+ * src_stride must be the kernel-reported bytesperline for the NV15 plane.
+ * The destination is dense P010 with row pitch = width * 2 bytes.
+ */
+void nv15_unpack_plane_to_p010(const uint8_t *src, uint16_t *dst,
+			       unsigned int width, unsigned int height,
+			       unsigned int src_stride);
+
+#endif