Add mission controller loading pipeline

[jackandcarter]

Motivation

• Provide a unified runtime pipeline to instantiate mission controllers and their pre-authored UI modules based on MissionDefinition assets.
• Allow each mission type to ship its own scene-built UI module and declare UI requirements instead of generating UI at runtime.
• Add a lightweight debug HUD and registry to speed iteration and testing of mission scenes.

Description

• Introduce the IMissionController interface and MissionUIRequirements / MissionUIModule types to standardize controller/ UI interactions and requirements.
• Add a MissionRegistry ScriptableObject to map MissionType values to controller prefabs and a MissionLoader MonoBehaviour that instantiates the controller and mission UI module and wires them together.
• Extend MissionDefinition with a UIModulePrefab reference so missions can reference scene-built UI modules, and update the Debris Navigation controller/HUD to implement IMissionController and derive the HUD from MissionUIModule.
• Add MissionDebugHUD for quick in-scene testing with succeed/fail buttons and runtime status display.

Testing

• No automated tests were executed as part of this change.
• Changes were compiled and staged in the working tree (9 files added/modified) but no CI run was performed.

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Codex Task