Add document frame render automation

docs/modernization/roadmap.md

@@ -453,9 +453,10 @@ duplicate selection masks.
 `pp_renderer_api` has started with renderer-neutral
 texture/readback descriptors and validation tests. `pp_paint_renderer` has
 started with deterministic CPU layer compositing over renderer extents using
-the paint blend reference, and now exposes a pure `pp_document` face
-compositor that expands per-layer dirty face payload rectangles into a full
-renderer-sized RGBA buffer for a requested frame/face. `pp_ui_core` has started with XML-layout-facing
+the paint blend reference, and now exposes pure `pp_document` face and
+six-face frame compositors that expand per-layer dirty face payload rectangles
+into full renderer-sized RGBA buffers for a requested document frame.
+`pp_ui_core` has started with XML-layout-facing
 length parsing, color parsing, tinyxml-backed layout XML parsing, and invalid
 input tests.
 `pano_cli inspect-image` exposes PNG IHDR metadata as JSON,
@@ -481,6 +482,8 @@ bytes using that writer, including PNG-encoded layer/frame face payloads.
 `pano_cli simulate-document-export` exercises that pure document export path,
 decodes the generated PPI bytes, reimports them, and emits JSON round-trip
 metadata.
+`pano_cli simulate-document-render` exercises the pure document-to-renderer
+frame compositor and emits six-face render summaries for headless automation.
 `pano_cli save-document-project` writes the same pure document export to a PPI
 file for inspect/load round-trip automation.
 `pano_cli create-document` can create simple animation documents with explicit
@@ -1703,7 +1706,8 @@ Results:
   no-feedback blends, invalid render-target usage, unsupported backends, and
   depth-target rejection.
 - `pp_paint_renderer_compositor_tests` passed, including pure
-  `pp_document` frame/face compositing over per-layer dirty face payloads.
+  `pp_document` face and six-face frame compositing over per-layer dirty face
+  payloads.
   The suite now covers fixed-function stroke composite planning,
   framebuffer-fetch planning, ping-pong texture-copy/blit fallback planning,
   dual/pattern blend feedback detection, invalid blend mode rejection,
@@ -1722,6 +1726,9 @@ Results:
 - `pano_cli_simulate_document_export_smoke` passed and reports pure
   `pp_document` export to PPI bytes, asset-level decode, and document reimport
   round-trip state as JSON.
+- `pano_cli_simulate_document_render_smoke` passed and reports pure
+  `pp_document` to `pp_paint_renderer` six-face frame compositing summaries as
+  JSON.
 - `pano_cli_simulate_image_import_smoke` passed and reports embedded PNG decode
   plus `pp_document` face-payload attachment state as JSON.
 - `pano_cli_inspect_image_rejects_unsupported` passed as an expected failure