Expose PNG metadata in pano cli

docs/modernization/build-inventory.md

@@ -89,6 +89,8 @@ Known local toolchain state:
   including foundation event/logging/task queue coverage, PNG metadata, PPI
   header, settings document, paint brush/stroke 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.
 - `panopainter_validate_shaders` validates the current combined GLSL shader
   files for one vertex stage marker, one fragment stage marker, valid marker
   order, and existing relative includes.