Agents run stylua/biome/rustfmt themselves, and a save-time reformat
races their in-flight writes to the same buffer. Timeout and LSP
fallback move to default_format_opts so <leader>fm (NvChad's binding)
keeps the same behaviour; conform now lazy-loads on first use.
Drops the /contrib/ skip — explicit invocation is already the opt-in.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>