Expose PNG metadata in pano cli

docs/modernization/roadmap.md

@@ -322,9 +322,10 @@ started with deterministic CPU layer compositing over renderer extents using
 the paint blend reference. `pp_ui_core` has started with XML-layout-facing
 length parsing, color parsing, tinyxml-backed layout XML parsing, and invalid
 input tests.
-`pano_cli parse-layout` now exercises that path. Continue expanding document
-behavior toward legacy Canvas parity and then port OpenGL classes behind the
-renderer boundary.
+`pano_cli inspect-image` exposes PNG IHDR metadata as JSON, and
+`pano_cli parse-layout` exercises the XML layout path. Continue expanding
+document behavior toward legacy Canvas parity and then port OpenGL classes
+behind the renderer boundary.
 
 Implementation tasks:
 
@@ -568,6 +569,8 @@ Results:
 - `pano_cli_create_document_smoke` passed.
 - `pano_cli_inspect_image_rejects_unsupported` passed as an expected failure
   test.
+- `pano_cli_inspect_png_metadata_smoke` passed and reports PNG metadata JSON
+  for the tiny IHDR fixture.
 - `pano_cli_parse_layout_smoke` passed.
 - `panopainter_validate_shaders` passed, validating 25 shader programs and 7
   shader includes for stage markers and include graph integrity.