stdlib ET does not cap entity expansion — a crafted .csproj or .lpk with nested
internal entities can exhaust memory. Pre-screen input bytes for <!DOCTYPE and
<!ENTITY before parsing (legitimate MSBuild/Lazarus files never contain these).
Also adds the missing 2 MiB size cap to extract_lpk (csproj already had one).
No new dependencies required.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>