[civilwarinfrance]

A UTF-8 byte-order mark at the start of an OBJ or MTL file becomes part of its first statement (v or newmtl). This can omit the first vertex/material, fail face loading, or raise an unimplemented-statement error in strict mode.

Resolve UTF-8 encoding aliases to the standard utf-8-sig decoder when opening plain or gzip files. It consumes only the initial signature; U+FEFF inside a material name remains intact. Keep the requested encoding setting and non-UTF-8 decoding unchanged. Document the behavior.

Validation on macOS/CPython 3.11.15:

• 24 regression cases fail on the original parser; 28 controls pass.
• All 143 project tests pass after the change, including 52 new cases for independent OBJ/MTL BOMs, plain/gzip files, default/explicit UTF-8 aliases, strict/non-strict parsing, UTF-16/Latin-1 and interior Unicode characters.
• CI blocking Flake8 check passes. Advisory check: 210 existing findings versus 211 on the base, no additions. New test file is lint-clean. git diff --check passes.

No dependencies are added. The older CI Python/OS matrix and rendering were not run locally.

AI assistance: OpenAI Codex prepared and tested this contribution.