MissionPlanner: add AI waypoint planner plugin

[Alico12315]

Summary

• Add an isolated .NET Framework 4.7.2 Mission Planner plugin under plugins/AIWaypointPlanner.
• Convert written mission requirements and optional reference files into locally validated candidate mission items.
• Support OpenAI-compatible Responses and Chat Completions endpoints, named connection profiles, local document processing and deterministic mission validation.
• Preserve the existing safety boundary: candidate rows are appended locally only; no flight-controller upload, mode change, arming, RC/PWM output or direct vehicle command is performed.

Compatibility and packaging

The current Mission Planner loader compiles top-level plugins/*.cs scripts. This change is supplied as a separate multi-file project because it uses external dependencies and an offline test assembly. Please advise whether it should be integrated into the main solution, adapted to the script loader or packaged separately.

Testing

• Release build against the installed Mission Planner host assemblies (net472) succeeded.
• AIWaypointPlanner.SelfTests.exe passed all offline tests, including endpoint validation, route and survey compilation, RTL enforcement, PDF/DOCX/PNG handling, request formatting, response capture and local-proxy diagnostics.

No live vehicle was connected and no mission was uploaded during testing.