[hzqst]

Zombie Panic 10210 requests the absent ui/icons/scoreboard/icon_dono0 image and immediately calls SetSize() on the result. Native VGUI returns a Bitmap for that request; the replacement scheme manager returned NULL and caused an access violation. Keep invalid Bitmaps in the cache and return them as native VGUI does; their existing Paint() path safely skips invalid textures.

Add a regression that calls native IBorder slots 6/7. It requires MetaHookSv/MetaHook#17, which removes ParseSideSettings from the public virtual interface. Merge that SDK fix first so standalone builds/tests consume the corrected header.

MetaHookSv/MetaHookSv#968 pins both component fixes and rebuilds their consumers together.

Validation with both component changes:

• Aggregate Debug/Win32 build with MSVC v143 and Windows SDK 10.0.26100.0 passed.
• All 11 CTests passed. The native-slot regression failed before the SDK fix and passed afterward.
• Pinned clang-format checks passed for both components.
• After deployment, CDB confirmed the missing-image request returned a VGUI2Extension Bitmap and the original zp client Start() returned without runtime patches.

Full halflife-mcp startup remains blocked later by Renderer's missing GameStudioRenderer_StudioDrawModel client symbol. This PR does not claim a successful main-menu/map/visual regression.