Preserve per-layer document timelines

docs/modernization/roadmap.md

@@ -321,8 +321,8 @@ CPU reference math for the five current shader blend modes, 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
-construction, layer metadata operations, frame move/duration queries, and
-layer/frame/undo-redo history invariant tests.
+construction, per-layer frame metadata, layer metadata operations, frame
+move/duration queries, and layer/frame/undo-redo history invariant tests.
 `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
@@ -332,8 +332,8 @@ input tests.
 `pano_cli inspect-image` exposes PNG IHDR metadata as JSON,
 `pano_cli inspect-project` reports validated PPI thumbnail/body byte layout,
 body summary, layer/frame descriptors, and dirty-face PNG payload metadata, and
-`pano_cli load-project` creates a metadata-only `pp_document` projection for
-representable PPI timelines.
+`pano_cli load-project` creates a metadata-only `pp_document` projection with
+per-layer frame counts and durations.
 `pano_cli create-document` can create simple animation documents with explicit
 frame count/duration, and `pano_cli simulate-stroke` exercises the pure stroke
 sampler for scripted-stroke automation. `pano_cli simulate-stroke-script`
@@ -581,7 +581,8 @@ Results:
 - `pp_paint_stroke_tests` passed.
 - `pp_paint_stroke_script_tests` passed.
 - `pp_document_tests` passed, including snapshot construction, alpha-lock
-  metadata, frame move, duration, and history invariants.
+  metadata, per-layer frame metadata, frame move, duration, and history
+  invariants.
 - `pp_renderer_api_tests` passed, including shader descriptor validation.
 - `pp_paint_renderer_compositor_tests` passed.
 - `pp_ui_core_color_tests` passed.
@@ -598,7 +599,8 @@ Results:
   thumbnail/body byte layout, body summary, layer/frame descriptors, and
   dirty-face PNG payload metadata JSON.
 - `pano_cli_load_project_metadata_smoke` passed and reports a metadata-only
-  `pp_document` projection for the minimal PPI fixture.
+  `pp_document` projection with per-layer frame counts and durations for the
+  minimal PPI fixture.
 - `pano_cli_parse_layout_smoke` passed.
 - `pano_cli_simulate_stroke_smoke` passed and reports deterministic stroke
   sample counts/distances.