Move stroke commit input binding behind service helper

docs/modernization/debt.md

@@ -108,6 +108,10 @@ 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 commit-input texture role switch through a local helper,
   leaving the callsite with sequence planning plus retained callback wiring.
+- 2026-06-13: `DEBT-0036` was narrowed again. `Canvas::stroke_commit()`
+  now routes the commit-input texture role switch through a retained service
+  helper, leaving the callsite with sequence planning and concrete face
+  bindings only.
 - 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

@@ -653,6 +653,9 @@ Progress Notes:
 - 2026-06-13: `Canvas::stroke_commit()` now routes the commit-input texture
   role switch through a local helper, so the callsite no longer owns that
   inline texture binding bundle.
+- 2026-06-13: `Canvas::stroke_commit()` now routes the commit-input texture
+  role switch through a retained service helper, so the callsite only supplies
+  concrete face bindings.
 - 2026-06-13: `Canvas::stroke_draw_samples()` now reuses a retained destination
   texture dispatch helper for the live sample path; `Canvas` still owns the
   concrete face textures and callback execution.

src/canvas.cpp

@@ -543,7 +543,7 @@ static auto make_canvas_stroke_commit_callbacks(
 {
     const auto& b = current_stroke->m_brush;
     auto bind_commit_inputs = [&](int i) {
-        pp::panopainter::bind_legacy_canvas_stroke_commit_inputs(
+        pp::panopainter::bind_legacy_canvas_stroke_commit_face_inputs(
             sequence,
             [&](int texture_slot) {
                 set_active_texture_unit(texture_slot);

src/legacy_canvas_stroke_commit_services.h

@@ -151,6 +151,20 @@ inline void bind_legacy_canvas_stroke_commit_inputs(
     }
 }
 
+template <typename SetActiveTextureUnit, typename BindFaceTextureRole, typename BindFaceSamplerRole>
+inline void bind_legacy_canvas_stroke_commit_face_inputs(
+    const pp::paint_renderer::CanvasStrokeCommitSequencePlan& sequence,
+    SetActiveTextureUnit&& set_active_texture_unit,
+    BindFaceTextureRole&& bind_face_texture_role,
+    BindFaceSamplerRole&& bind_face_sampler_role)
+{
+    bind_legacy_canvas_stroke_commit_inputs(
+        sequence,
+        std::forward<SetActiveTextureUnit>(set_active_texture_unit),
+        std::forward<BindFaceTextureRole>(bind_face_texture_role),
+        std::forward<BindFaceSamplerRole>(bind_face_sampler_role));
+}
+
 template <typename SetupShader, typename DrawPlane>
 inline void execute_legacy_canvas_stroke_commit_erase(
     SetupShader&& setup_shader,