Add stroke alpha blend reference tests

docs/modernization/build-inventory.md

@@ -94,8 +94,8 @@ Known local toolchain state:
   including foundation event/logging/task queue coverage, PNG metadata and
   decode, PPI header/layout, settings document, document
   snapshot/per-layer-frame/move/duration/face-pixel/PPI export coverage,
-  snapshot-embedded face-payload rejection, paint brush/stroke/stroke-script
-  coverage, renderer shader descriptor and OpenGL capability coverage, UI
+  snapshot-embedded face-payload rejection, paint brush/final-blend/
+  stroke-alpha-blend/stroke/stroke-script coverage, renderer shader descriptor and OpenGL capability coverage, UI
   color parsing, and layout XML parse coverage.
 - `pano_cli inspect-image` reports PNG IHDR metadata as JSON and is covered by
   `pano_cli_inspect_png_metadata_smoke` with a tiny IHDR fixture.

docs/modernization/capability-map.md

@@ -34,8 +34,8 @@ and validation command.
 | ABR import | `ABR`, `Brush` | `pp_assets`, `pp_paint` | Sample ABR and malformed ABR |
 | PPBR import/export | brush panel/dialog | `pp_assets`, `pp_panopainter_ui` | Round-trip fixture |
 | Stroke sampling | `Stroke`, `Canvas` | `pp_paint` | Property tests for spacing, pressure, jitter |
-| Dual brush/pattern behavior | `Brush`, shaders | `pp_paint`, `pp_paint_renderer` | CPU reference and GPU golden |
-| Blend modes | GLSL include files, layer rendering | `pp_paint`, `pp_paint_renderer` | CPU reference vectors and GPU parity |
+| Dual brush/pattern behavior | `Brush`, shaders | `pp_paint`, `pp_paint_renderer` | Stroke-alpha CPU reference and GPU golden |
+| Blend modes | GLSL include files, layer rendering | `pp_paint`, `pp_paint_renderer` | Final RGBA and stroke-alpha CPU reference vectors plus GPU parity |
 | Erase/flood fill/masks | `Canvas`, modes, shaders | `pp_document`, `pp_paint_renderer` | Edge masks, alpha lock, dirty rects |
 
 ## Layers And Animation
@@ -80,4 +80,3 @@ and validation command.
 | Logging/crash reporting | `log`, BugTrap/AppCenter | `pp_foundation`, platform wrappers | Log formatting and platform compile |
 | Headless automation | none yet | `tools/pano_cli` | JSON command fixtures |
 | Tracing | none yet | `pp_foundation` | Span nesting/timing tests |
-

docs/modernization/roadmap.md

@@ -318,7 +318,8 @@ asset-level RGBA PNG payload decoding, and a pure typed settings document
 model, with
 corrupt/truncated/unsupported, extreme-dimension, and key/value limit tests.
 `pp_paint` has started with pure brush parameter validation/stamp evaluation,
-CPU reference math for the five current shader blend modes, and deterministic
+CPU reference math for the five current final RGBA shader blend modes plus the
+shader-style stroke-alpha blend modes used by pattern/dual-brush mixing, and deterministic
 stroke spacing/interpolation plus a pure text stroke-script parser.
 `pp_document` has
 started with a pure canvas/layer/frame model, alpha-lock metadata, snapshot
@@ -537,7 +538,7 @@ Implementation tasks:
   - layer blend
   - equirect export
   - readback bounds
-- Add CPU reference tests for blend modes.
+- Add CPU reference tests for final RGBA and stroke-alpha blend modes.
 - Compare GPU output to golden/reference data with explicit tolerances.
 
 Gate: