Fix MPH briefing adaptive widescreen

[MysteriousAeon]

Fixes the Metroid Prime Hunters mission briefing/text-scroll being incorrectly treated as an adaptive widescreen gameplay scene.

The MPH frontend can transition into a display configuration that satisfies the generic adaptive compositor's supported-scene checks during the briefing. This causes the full-screen briefing artwork and HUD/OBJ elements to be remapped across the widened output.

This adds an AMHE0-specific briefing scene predicate and routes that scene through the existing centered-native fallback while leaving normal adaptive gameplay unchanged.

The predicate is gated by:

• the exact AMHE0 ROM
• the frontend overlay identity
• the frontend menu list
• the mission briefing menu entry

It is latched at the existing frame boundary before presentation.

Also updates the focused GPU2D test harness for the new title-policy dependency.

Validation:

• Release build passes on Linux
• 15/15 CTest tests pass
• git diff --check passes

Fixes mstan/MetroidPrimeHuntersRecomp#29