forgectrl pinned at the bench-proven GPU path; the session's record

The pin moves to forgectrl 6614833: the five hardware corrections from
the GPU demosaic's first bench session (surfaceless EGL config, ARGB
render targets, GR88 raw import, the ipu_copy stride-fix crop between
the GPU and the CODA, the chroma mirror width). CAMPAIGN-LOG carries
the dated record of how each was found; BRINGUP item 20 now separates
what that session proved (the full GPU -> IPU -> VPU path serving
correct frames, H.264 as valid fragmented MP4 on hardware, texture
limits, slot fit) from what remains (the 140 ms render, the bottom
row, MSE playback, the CPU measurement, frame skip, coexistence, the
campaign).

docs/CAMPAIGN-LOG.md

@@ -3630,6 +3630,45 @@ on the bed, and the two together by one real print. Still open from that
 plan: the bench actuator for the lid, interlock and button, and the
 finer coverage maps.
 
+## 2026-08-24: the GPU demosaic's first light, and what the probes caught
+
+Dev image 20260824122014 (the first with Mesa etnaviv; release ext4
+204,140,544 bytes, ~5 MiB under the slot cap) flashed by the operator;
+the drill ran forgectrl builds from `/tmp` against the running image,
+each iteration probed over the stream, `FORGECTRL_GPU_CHECK`, and frame
+captures diffed against the CPU demosaic on the host.
+
+Five faults found and fixed in one session, each named by a probe log
+line or the compare (forgectrl 6614833):
+
+1. `eglChooseConfig` returned nothing: EGL_SURFACE_TYPE defaults to
+   WINDOW_BIT and the surfaceless platform has no window configs. Ask
+   for surface type 0.
+2. Every fourth output byte was 255: the render engine writes an
+   XRGB8888 surface's undefined X byte as opaque. Render ARGB8888.
+3. The raw import failed etnaviv's stride check (width padded to 16
+   texels): 2592 bytes is 1296 GR88 texels exactly, not 656 padded
+   XRGB ones. Import GR88, one texel per Bayer pair.
+4. The GPU cannot write the CODA's buffers at all: 64-byte render rows
+   versus round_up(width,16) strides never meet at these widths. New
+   `ipu_copy` module: render into the IPU CSC/scaler's wider source
+   (stride align(w,128)) and let the IPU crop into each encoder over
+   dmabuf. 14 ms a copy, no CPU touch.
+5. The chroma mirror used a quarter-width plane where the plane is
+   half-width: the right half of both chroma planes clamped to
+   column 0. The three-frame diff-by-transform analysis on the host
+   named both this and fault 2.
+
+End state on the bench: `convert: "gpu"` serving MJPEG, the GPU/CPU
+compare clean to 2 counts except the bottom row (1296 samples, max
+delta 134, unexplained); `/cam/h264` delivering valid fragmented MP4
+from the CODA BIT processor (avc1.424020, ~480 kbit/s on the static
+bed). Open, measured: the render costs 140 ms a frame against the IPU's
+14 (GPU at its full 528 MHz - the suspicion is pre-HALTI linear-texture
+sampling), so the GPU path holds ~6 fps until that is run down. The
+`getenv` implicit-declaration fix in debayer.c rode along. Bench left
+clean; stock service restored.
+
 ## Superseded status notes
 
 ### Shared machine services — remaining polish, as listed 2026-08-13