OpenSKP Import/Export

### 🔌 𝗥𝗲𝗽𝗼𝘀𝗶𝘁𝗼𝗿𝘆

https://github.com/iamahsanmehmood/freecad-openskp

### 📑 𝗡𝗼𝘁𝗲𝘀

Native SketchUp (.skp) import and export for FreeCAD - no Trimble SDK, no SketchUp installation, no compiled extension required. Built on OpenSKP (github.com/iamahsanmehmood/openskp), a from-scratch, MIT-licensed .skp reader/writer.

What it does:
- Import: real B-rep geometry (planar faces/loops via Part.Face/Part.Compound, not a triangulated mesh), full placed scene graph (components/groups/nested instances) with per-unique-definition caching, loose-edge/structural-framing import, materials (per-face color), and layers (SketchUp tags) - one object per layer, with correct visibility.
- Export: flattens selected FreeCAD objects back to a .skp file, including layers and materials in both directions now.
- Performance-tested on real production files up to 358K faces (numbers in the README).

Testing so far: exercised against several real, non-trivial production .skp files (a 358K-face building model, a 145-definition structural-framing/light-gauge-steel model) plus a real external user who has downloaded and used multiple releases, filing and confirming fixes for real bugs along the way. Automated test suite runs on every push via GitHub Actions.

Repo: https://github.com/iamahsanmehmood/freecad-openskp
Latest release: v0.2.4

Review the linked freecad-openskp repository, its README, latest release v0.2.4, and GitHub Actions results first. Then inspect how the FreeCAD Addons index represents addon submissions; done means the OpenSKP addon is documented and accepted there with its repository and release details.

Written by the indexing model from the issue text.