Enhance mission UI generator wiring

[jackandcarter]

Motivation

• Improve the editor UI generator so generated mission UI is wired to the scene-level mission systems automatically.
• Reduce manual scene setup by ensuring a MissionLoader/scene root and MissionUIManager exist or are created.
• Surface missing HUD/controller bindings to the user immediately after generation to reduce runtime mismatches.
• Encode mission-specific wiring expectations so the generator can make best-effort connections for each MissionType.

Description

• Added a post-generation step PostProcessMissionSetup(...) to Assets/Editor/MissionUIGeneratorWindow.cs that performs mission-specific wiring and validation.
• The generator now ensures a MissionLoader/scene root (instantiating Assets/Missions/Prefabs/M2SceneRoot.prefab or creating a root), and attempts to assign or locate a MissionRegistry.
• Implemented mission-controller discovery/creation, controller-prefab discovery and registration into MissionRegistry, and controller-to-HUD field wiring helpers.
• Added an in-code MissionUISpec mapping that documents per-MissionType expected UI module type, required HUD serialized fields, controller type, and controller HUD field names used for validation and wiring.

Testing

• No automated tests were run for this change.
• Changes are editor tooling only and should be validated in the Unity Editor by running M2 → Tools → Mission UI Generator and verifying dialogs and scene wiring.
• No CI or playmode tests were executed as part of this PR.
• Please run the Unity editor to compile and verify inspector/serialized-field behavior after merging.

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Codex Task