AI Assistant: initial skeleton + v0.1.0 contract + dockable panel scaffold

[Coben-3d]

Summary

This PR introduces the initial foundations for an integrated AI Slice Assistant in OrcaSlicer.

Included in this PR

• Adds the initial folder structure for the AI assistant (src/ai/, docs/ai/, etc.)
• Adds contract documentation and a strict v0.1.0 JSON response schema
• Adds a minimal dockable wxWidgets panel: AI Slice Assistant
  • Menu toggle to show/hide the panel
  • Basic local chat UI (no networking yet)

Scope / Notes

• No AI provider is implemented yet
• No slicing settings are modified
• This is intentionally a minimal scaffolding PR to enable incremental development

Next steps

• Context snapshot builder (100+ settings, read-only)
• Fake provider + validation pipeline
• Allowlist + diff/apply/undo
• OpenAI-compatible provider + preferences UI