chore(repo): 🔥 un-track 65k build artifacts (~25GB) and extend gitignore
Build artifacts got committed before gitignore rules existed.
Removes from git index (working-tree files unchanged):
- src/simulator/target/ (65,283 files, ~25GB)
- magic_civ_physics/*.{so,dylib} (wrong-arch confusion risk)
- tools/sprite-generation/*.db* (host-local SQLite)
- .playwright-mcp/ (per-session test snapshots)
- *.pyc files (Python bytecode)
Adds gitignore rules for .playwright-mcp/, *.pyc, and sprite-gen *.db*
so re-adds don't happen.
Each host builds its own target/ and .so/.dylib going forward.