inspect_managed_native_boundaries derived summary.mixed_mode_or_native_header
only from the managed native header and the native entry-point flag. A C++/CLI
assembly with ILONLY clear and no ReadyToRun signature was classified as
mixed-clr-native by inspect_managed_artifact but summarized as not mixed.
Give the rule one owner, managedCliIsMixedClrNative in ManagedPeReader, and
use it for both the artifact runtime family and the boundary summary. The
summary now reads the CLI header directly instead of the cli_native projection.
Fixes#3366
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
