Move stroke commit request assembly behind service helper

docs/modernization/debt.md

@@ -115,6 +115,10 @@ agent or engineer to remove them without reconstructing context from chat.
 - 2026-06-13: `DEBT-0036` was narrowed again. `Canvas::stroke_commit()`
   now routes the face-indexed commit-input binding wrapper through the retained
   service boundary, leaving `Canvas` with only concrete face bindings.
+- 2026-06-13: `DEBT-0036` was narrowed again. `Canvas::stroke_commit()`
+  now routes the retained commit request assembly through
+  `make_legacy_canvas_stroke_commit_request(...)`, leaving the callsite with
+  only concrete faces, sequence, and callbacks.
 - 2026-06-13: `DEBT-0036` was narrowed again. `NodeStrokePreview::draw_stroke_immediate()`
   now routes final composite execution and preview copy-back through a retained
   local wrapper, leaving the call site with only sequence wiring.

docs/modernization/tasks.md

@@ -1253,6 +1253,10 @@ ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_stroke_ex
 | --- | --- | ---: | --- | --- |
 | 2026-06-13 | STR-014 | +1 renderer boundary and OpenGL parity | `ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_stroke_execution|pp_paint_renderer_compositor" --output-on-failure` | `536f2683` |
 
+- 2026-06-13: `Canvas::stroke_commit()` now routes the retained commit request
+  assembly through `make_legacy_canvas_stroke_commit_request(...)`, so the
+  callsite only supplies concrete faces, sequence, and callbacks.
+
 ### STR-011 - Extract Preview Main Pass Orchestration
 
 Status: Done

src/canvas.cpp

@@ -736,19 +736,6 @@ static auto make_canvas_stroke_commit_callbacks(
         });
 }
 
-static auto make_canvas_stroke_commit_request(
-    const std::array<pp::panopainter::LegacyCanvasStrokeCommitFace, 6>& faces,
-    const pp::paint_renderer::CanvasStrokeCommitSequencePlan& sequence,
-    const pp::panopainter::LegacyCanvasStrokeCommitCallbacks& callbacks)
-{
-    return pp::panopainter::LegacyCanvasStrokeCommitRequest {
-        .context = "Canvas::stroke_commit",
-        .faces = faces,
-        .sequence = sequence,
-        .callbacks = callbacks,
-    };
-}
-
 glm::vec4 Canvas::stroke_draw_samples(
     int i,
     std::vector<vertex_t>& P,
@@ -1353,7 +1340,7 @@ void Canvas::stroke_commit()
     };
 
     [[maybe_unused]] const auto commit_result = pp::panopainter::execute_legacy_canvas_stroke_commit_sequence(
-        make_canvas_stroke_commit_request(faces, sequence, commit_callbacks));
+        pp::panopainter::make_legacy_canvas_stroke_commit_request(faces, sequence, commit_callbacks));
 }
 
 void Canvas::stroke_commit_timelapse()

src/legacy_canvas_stroke_commit_services.h

@@ -165,6 +165,19 @@ inline void bind_legacy_canvas_stroke_commit_face_inputs(
         std::forward<BindFaceSamplerRole>(bind_face_sampler_role));
 }
 
+[[nodiscard]] inline LegacyCanvasStrokeCommitRequest make_legacy_canvas_stroke_commit_request(
+    const std::array<LegacyCanvasStrokeCommitFace, 6>& faces,
+    const pp::paint_renderer::CanvasStrokeCommitSequencePlan& sequence,
+    const LegacyCanvasStrokeCommitCallbacks& callbacks)
+{
+    return LegacyCanvasStrokeCommitRequest {
+        .context = "Canvas::stroke_commit",
+        .faces = faces,
+        .sequence = sequence,
+        .callbacks = callbacks,
+    };
+}
+
 template <typename SetupShader, typename DrawPlane>
 inline void execute_legacy_canvas_stroke_commit_erase(
     SetupShader&& setup_shader,

tests/paint_renderer/compositor_tests.cpp

@@ -1972,6 +1972,55 @@ void retained_stroke_commit_request_builder_preserves_dirty_face_order(pp::tests
     PP_EXPECT(h, request.faces[5].index == 5);
 }
 
+void retained_stroke_commit_request_helper_preserves_dirty_face_order(pp::tests::Harness& h)
+{
+    const pp::panopainter::LegacyCanvasStrokeCommitCallbacks callbacks {
+        .mark_commit_started = []() {},
+        .capture_render_state = []() {},
+        .prepare_render_state = []() {},
+        .restore_render_state = []() {},
+        .publish_history = []() {},
+        .capture_timelapse_frame = []() {},
+        .bind_layer_framebuffer = [](int) {},
+        .capture_history_region = [](int) {},
+        .apply_layer_dirty_region = [](int) {},
+        .copy_layer_to_commit_destination = [](int) {},
+        .bind_commit_inputs = [](int) {},
+        .execute_erase_composite = [](int) {},
+        .execute_paint_composite = [](int) {},
+        .copy_committed_to_dilate_source = [](int) {},
+        .execute_commit_dilate = [](int) {},
+        .unbind_layer_framebuffer = [](int) {},
+    };
+    const auto sequence = plan_canvas_stroke_commit_sequence(
+        CanvasStrokeCommitRequest {
+            .erase_mode = true,
+            .alpha_locked = true,
+            .selection_mask_active = false,
+            .dual_stroke_enabled = false,
+            .pattern_enabled = false,
+        });
+    const std::array<pp::panopainter::LegacyCanvasStrokeCommitFace, 6> faces {
+        pp::panopainter::LegacyCanvasStrokeCommitFace { .index = 0, .dirty = true },
+        pp::panopainter::LegacyCanvasStrokeCommitFace { .index = 1, .dirty = false },
+        pp::panopainter::LegacyCanvasStrokeCommitFace { .index = 2, .dirty = true },
+        pp::panopainter::LegacyCanvasStrokeCommitFace { .index = 3, .dirty = false },
+        pp::panopainter::LegacyCanvasStrokeCommitFace { .index = 4, .dirty = true },
+        pp::panopainter::LegacyCanvasStrokeCommitFace { .index = 5, .dirty = false },
+    };
+
+    const auto request = pp::panopainter::make_legacy_canvas_stroke_commit_request(
+        faces,
+        sequence,
+        callbacks);
+
+    PP_EXPECT(h, request.context == "Canvas::stroke_commit");
+    PP_EXPECT(h, request.faces[0].dirty);
+    PP_EXPECT(h, request.faces[1].index == 1);
+    PP_EXPECT(h, request.faces[2].dirty);
+    PP_EXPECT(h, request.faces[4].dirty);
+}
+
 void retained_stroke_commit_dilate_copy_uses_layer_scratch_slot(pp::tests::Harness& h)
 {
     const auto sequence = plan_canvas_stroke_commit_sequence(