Add image export roundtrip automation

docs/modernization/build-inventory.md

@@ -98,17 +98,21 @@ Known local toolchain state:
   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.
+- `pp_assets_image_pixels_tests` decodes PNG payloads, encodes RGBA8 pixels to
+  PNG, round-trips encoded pixels back through the decoder, and rejects corrupt
+  or malformed image payloads.
 - `pano_cli import-image` accepts a PNG path, decodes RGBA8 pixels through
   `pp_assets`, attaches them to a pure `pp_document` face payload, and is
   covered for checked-in decodable PNG import by `pano_cli_import_image_smoke`
   and metadata-valid truncated PNG rejection by
   `pano_cli_import_image_rejects_truncated_png`.
+- `pano_cli export-image` writes a deterministic RGBA8 PNG through `pp_assets`
+  and is covered by `pano_cli_export_image_roundtrip_smoke`, which imports the
+  generated file back through `pano_cli import-image`.
 - `pano_cli inspect-project` reports validated PPI thumbnail/body byte layout,
   body summary fields, layer/frame descriptors, and dirty-face PNG payload
   metadata, and is covered by `pano_cli_inspect_project_layout_smoke` with a
   minimal PPI fixture.
-- `pp_assets_image_pixels_tests` decodes PNG payloads to RGBA8 and rejects
-  corrupt image payloads.
 - `pp_document_ppi_import_tests` attaches decoded PPI dirty-face payloads to
   `pp_document` layer/frame storage and rejects payloads outside document
   layers.
@@ -275,8 +279,10 @@ Known local toolchain state:
 - `pano_cli import-image` exposes file-driven PNG decode and document
   face-payload attachment through JSON automation and is covered by
   `pano_cli_import_image_smoke` and
-  `pano_cli_import_image_rejects_truncated_png`; export/round-trip automation
-  remains a future CLI task.
+  `pano_cli_import_image_rejects_truncated_png`.
+- `pano_cli export-image` exposes deterministic RGBA8 PNG writing through JSON
+  automation and is covered by `pano_cli_export_image_roundtrip_smoke`; full
+  legacy canvas export remains a future CLI task.
 - `pano_cli save-project` exposes generated multi-layer, multi-frame PPI writing through JSON
   automation and is covered by metadata-only and dirty-face-payload round-trip
   smoke tests; full legacy canvas save parity remains tracked by

docs/modernization/roadmap.md

@@ -335,6 +335,8 @@ input tests.
 `pano_cli import-image` accepts a PNG path and imports decoded RGBA8 pixels
 into a new pure `pp_document` face payload,
 with checked-in decodable PNG and truncated PNG automation coverage,
+`pano_cli export-image` writes a deterministic RGBA8 PNG through `pp_assets`
+and round-trips it back through file import automation,
 `pano_cli inspect-project` reports validated PPI thumbnail/body byte layout,
 body summary, layer/frame descriptors, dirty-face PNG payload metadata, and
 asset-level decode coverage, and
@@ -785,8 +787,10 @@ Results:
   automation.
 - `pano_cli import-image` accepts a PNG file path, decodes RGBA8 pixels through
   `pp_assets`, attaches them to a pure `pp_document` face payload, and has
-  checked-in decodable-PNG plus truncated-PNG rejection smoke tests. Full
-  export/round-trip automation remains a future `pano_cli` task.
+  checked-in decodable-PNG plus truncated-PNG rejection smoke tests.
+- `pano_cli export-image` writes deterministic RGBA8 PNGs through `pp_assets`
+  and has a save/import round-trip smoke test. Full legacy canvas export
+  remains a future `pano_cli` task.
 - `pano_cli save-project` exposes generated multi-layer, multi-frame PPI writing through JSON
   automation and is covered by metadata-only and dirty-face-payload save/load
   round-trip smoke tests. Full legacy canvas save parity remains