Effects: OCIO custom configs read Blender's v2 transforms and warn (#410)

Cause: the config reader didn't know ColorSpaceTransform or
ExponentWithLinearTransform and passed colours through them silently.
Blender's Linear Rec.709 -> sRGB therefore stayed in its E-white XYZ
reference space (the blue cast) without the sRGB curve. Display
colorspaces, view transforms, v2 views, looks, AllocationTransform,
BuiltinTransform and .spi1d / .spimtx files were missing too, and
nothing told the user.

Fix (from the OCIO v2 documentation and the CLF "moncurve", not OCIO's
source): ExponentWithLinear, ColorSpace, Look, DisplayView, Allocation
and Builtin transforms (identity, ACES AP0/AP1 matrices, ACEScct /
ACEScc, the sRGB / P3 / Rec.1886 / gamma / PQ displays). RangeTransform
now clamps and takes one-sided ranges. Display colorspaces meet the
scene reference through the default view transform. Added v2 views,
view looks, the looks section and .spi1d / .spi3d / .spimtx files. A
conversion is built once as a flat list of steps (Config::path /
display_path) for both the CPU effect and the GPU colour program (new
moncurve and clamp ops and the ACEScc curve; a program over the
kernel's 255 ops renders on the CPU). Named-transform resolution is
limited to 16 levels and 4096 steps, and YAML nesting to 64 levels, so
hostile or looping configs stop. Transforms that are still unsupported
(Grading Primary / Tone, ACES output, HLG…), unreadable configs and
unknown spaces are now reported: a warning under the effect in Effect
Controls, and the new effect.warning query.

Tests: ocio_config::blender_like_config_converts_linear_rec709_to_srgb
(CST, display colorspaces, v1 / v2 views, allocation, looks, builtin,
range, loops), moncurve_matches_srgb_and_inverts, builtin_styles,
yaml_nesting_is_bounded, ocio::spi_files_parse,
tests_effects::ocio_effect_warns_about_unsupported_config_transforms,
gpu tests_fx_lut::ocio_custom_config_v2 (GPU = CPU).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/agents.md

@@ -222,6 +222,9 @@ build real projects through these interfaces; they are worked examples of everyt
 * **Colour of footage**: `file.interpretFootage {"items":[id], "preserveRgb":true}` is Interpret
   Footage ▸ Preserve RGB: the file's values unconverted (float EXRs stay linear), for a
   per-layer OCIO conversion or data passes.
+* **OCIO effects**: with Configuration ▸ Custom, `configFile` is a `.ocio` path or the config's
+  text; `effect.warning {layer, effect}` says what Effect Controls warns about (a config it
+  can't read, a colour space it lacks, transforms that pass colours through) or `null`.
 * **Multi-layer OpenEXR**: the footage shows the beauty pass (an unnamed RGBA layer, else
   Combined / Beauty / Image / RGBA…, never Cryptomatte or depth). `layer.channels {layer}`
   lists a footage layer's EXR layers and

docs/parity.md

@@ -192,7 +192,7 @@ Mocha and Cineware are third-party and not counted.
 |---|---|---|
 | 3D Channel | 3D Channel Extract, Cryptomatte, Depth Matte, Depth of Field, EXtractoR, Fog 3D, ID Matte, IDentifier | Read auxiliary channels: multi-layer OpenEXR (any `layer.channel`, Cryptomatte manifests from the header; EXtractoR picks a layer and channels from popups of the footage's layers and channels, `layer.channels`, #295; the footage itself shows the beauty pass, never Cryptomatte or depth, #412) or the compositor's own depth / layer-ID / normal / UV / Cryptomatte pass for precomps of 3D comps. |
 | Immersive Video | VR Blur, VR Chromatic Aberrations, VR Color Gradients, VR Converter, VR De-Noise, VR Digital Glitch, VR Fractal Noise, VR Glow, VR Plane to Sphere, VR Rotate Sphere, VR Sharpen, VR Sphere to Plane | Seam-aware equirectangular processing (wrap-around, pole continuation, latitude-scaled filters), mono / over-under / side-by-side layouts; VR Converter between equirectangular, cube maps (4:3, 3:2, 6:1), sphere map and 2D. |
-| Color Correction | OCIO CDL / Color Space / Display / File / Look Transform, Color Stabilizer | Built-in minimal OCIO-style config (ACES2065-1, ACEScg, ACEScct, sRGB, Rec.709, Rec.2020, Display P3, linear variants, XYZ) from published matrices and transfer functions; `.cube` / `.3dl` / `.csp` LUTs and ASC `.cc` / `.ccc` / `.cdl`. Custom `.ocio` config files are read (Configuration ▸ Custom: colorspaces, roles, displays/views; Matrix, File, Exponent, Log, LogAffine, CDL, Range and Group transforms). |
+| Color Correction | OCIO CDL / Color Space / Display / File / Look Transform, Color Stabilizer | Built-in minimal OCIO-style config (ACES2065-1, ACEScg, ACEScct, sRGB, Rec.709, Rec.2020, Display P3, linear variants, XYZ) from published matrices and transfer functions; `.cube` / `.3dl` / `.csp` / `.spi1d` / `.spi3d` / `.spimtx` LUTs and ASC `.cc` / `.ccc` / `.cdl`. Custom `.ocio` config files are read from the OCIO v2 documentation (Configuration ▸ Custom: colorspaces and display colorspaces with the scene / display reference spaces joined by the default view transform, roles, displays with v1 and v2 views, view transforms, looks; Matrix, File, Exponent, ExponentWithLinear, Log, LogAffine, CDL, Range, Allocation, ColorSpace, Look, DisplayView, Builtin (matrices and display curves) and Group transforms), so Blender 4.x / 5.x configs give the Standard, AgX, Filmic and False Color views (#410). Grading Primary / Tone transforms, the ACES output and gamut-compression builtins and HLG pass colours through, and the effect shows a warning naming them (`effect.warning`). |
 | Distort | CC Flo Motion, Liquify, Rolling Shutter Repair | Liquify strokes are effect data replayed into a displacement mesh (`liquify.stroke` / `liquify.clear` commands; no interactive viewer brush yet). Rolling Shutter Repair uses the KLT tracker. |
 | Blur & Sharpen | Camera-Shake Deblur, CC Radial Blur | Deblur substitutes aligned patches from sharper neighbouring frames. |
 | Audio | Compressor, Distortion, Gate | Applied in the mixdown like the other audio effects. |
@@ -753,7 +753,8 @@ composited at 8 and 32 bpc:
   cineSpace shapers are read from a storage buffer with the CPU's nearest / trilinear /
   tetrahedral interpolation and inverses (not a hardware 3D texture: its filtering rounds the
   weights and cannot do tetrahedral). Lumetri's Input LUT and Look no longer force the CPU.
-  Custom `.ocio` configurations render on the CPU. Exception: nearest-neighbour lattice lookups
+  Custom `.ocio` configurations compile to the same programs (one of more than 255 steps
+  renders on the CPU). Exception: nearest-neighbour lattice lookups
   may pick the other lattice point for 8 bpc inputs exactly on a rounding boundary (up to 1 %
   of pixels allowed).
 - **Simulation render passes** (`gpu::fx_sim`): CC Rainfall, CC Snowfall, CC Star Burst, CC