Add PPI header recognition tests

docs/modernization/build-inventory.md

@@ -78,7 +78,7 @@ Known local toolchain state:
   `platform-build` automation wrapper for `pp_foundation`, `pp_assets`,
   `pp_paint`, `pp_document`, `pp_renderer_api`, `pp_paint_renderer`,
   `pp_ui_core`, `pano_cli`, and their current headless test binaries,
-  including layout XML parse coverage.
+  including PPI header and layout XML parse coverage.
 - `vcpkg` is not on PATH yet; see DEBT-0007.
 
 Known warnings after the current CMake app build:

docs/modernization/debt.md

@@ -31,6 +31,7 @@ agent or engineer to remove them without reconstructing context from chat.
 | DEBT-0010 | Open | Modernization | `pp_document` is a pure layer/frame/document model but is not yet wired to legacy `Canvas`, PPI load/save, selection masks, or undo/redo | Keep extraction incremental while preserving app behavior | `ctest --preset desktop-fast --build-config Debug`; `pano_cli create-document --width 64 --height 32 --layers 2` | Legacy document behavior is represented by `pp_document` tests and the app consumes it through a boundary/facade |
 | DEBT-0011 | Open | Modernization | `package-smoke` validates the Windows CMake app artifact only, not AppX/APK/Apple/WebGL package outputs | Platform package targets are not migrated to root CMake yet | `powershell -ExecutionPolicy Bypass -File scripts\automation\package-smoke.ps1 -Preset windows-msvc-default -Configuration Debug` | Package-smoke covers Windows AppX, Android APK variants, Apple bundles, and WebGL output where local toolchains are present |
 | DEBT-0012 | Open | Modernization | `pp_vendor_tinyxml2` compiles the retained vendored tinyxml2 copy for `pp_ui_core` layout parsing | vcpkg is not validated yet, but layout parsing needs a structured XML parser now | `ctest --preset desktop-fast --build-config Debug`; `powershell -ExecutionPolicy Bypass -File scripts\automation\platform-build.ps1 -Presets android-arm64` | Replace with vcpkg tinyxml2 target once desktop and mobile triplets are validated |
+| DEBT-0013 | Open | Modernization | `pp_assets` and `pano_cli inspect-project` recognize only the fixed PPI header, not thumbnail bytes or the project body | Full PPI parsing requires staged extraction of legacy `Canvas` serialization and image/layer payload handling | `ctest --preset desktop-fast --build-config Debug`; `pp_assets_ppi_header_tests` | Full PPI load/save fixtures cover thumbnail, layers, frames, metadata, corrupt payloads, and round-trip compatibility |
 
 ## Closed Debt
 

docs/modernization/roadmap.md

@@ -245,8 +245,9 @@ Status: in progress. `tests/` exists, `desktop-fast` runs headlessly, and
 PowerShell/bash wrappers exist for
 configure/build/test/analyze/platform-build/package-smoke. `pano_cli` exists
 with JSON automation commands for creating a `pp_document` model and
-inspecting image signatures; full document/app integration is debt-tracked as
-DEBT-0010.
+inspecting image signatures, PPI headers, and layout XML; full document/app
+integration is debt-tracked as DEBT-0010 and full PPI body parsing is
+debt-tracked as DEBT-0013.
 
 Implementation tasks:
 
@@ -304,7 +305,8 @@ boundary/overread tests. It also owns strict decimal `uint32` parsing used by
 `pano_cli`, with rejection tests for empty, signed, mixed, and overflowing
 input. A deterministic `TraceRecorder` now records component/name/thread/frame
 and stroke timing spans with invalid-end tests. `pp_assets` has started with
-PNG/JPEG signature detection and corrupt/truncated/unsupported tests.
+PNG/JPEG signature detection plus PPI header recognition, with
+corrupt/truncated/unsupported tests.
 `pp_paint` has started with CPU reference math for the five current shader
 blend modes. `pp_document` has started with a pure canvas/layer/frame model
 and layer/frame invariant tests. `pp_renderer_api` has started with renderer-neutral
@@ -518,7 +520,7 @@ Last verified on 2026-06-01:
 
 ```powershell
 cmake --preset windows-msvc-default
-cmake --build --preset windows-msvc-default --config Debug --target pp_foundation_binary_stream_tests pp_foundation_parse_tests pp_foundation_trace_tests pp_assets_image_format_tests pp_paint_blend_tests pp_document_tests pp_renderer_api_tests pp_paint_renderer_compositor_tests pp_ui_core_layout_value_tests pp_ui_core_layout_xml_tests pano_cli PanoPainter
+cmake --build --preset windows-msvc-default --config Debug --target pp_foundation_binary_stream_tests pp_foundation_parse_tests pp_foundation_trace_tests pp_assets_image_format_tests pp_assets_ppi_header_tests pp_paint_blend_tests pp_document_tests pp_renderer_api_tests pp_paint_renderer_compositor_tests pp_ui_core_layout_value_tests pp_ui_core_layout_xml_tests pano_cli PanoPainter
 ctest --preset desktop-fast --build-config Debug
 powershell -ExecutionPolicy Bypass -File scripts\automation\test.ps1 -Preset desktop-fast -Configuration Debug
 powershell -ExecutionPolicy Bypass -File scripts\automation\build.ps1 -Preset windows-msvc-default -Configuration Debug -Target pano_cli
@@ -533,6 +535,7 @@ Results:
 - `pp_foundation_parse_tests` passed.
 - `pp_foundation_trace_tests` passed.
 - `pp_assets_image_format_tests` passed.
+- `pp_assets_ppi_header_tests` passed.
 - `pp_paint_blend_tests` passed.
 - `pp_document_tests` passed.
 - `pp_renderer_api_tests` passed.