Enforce LF endings for text files

[mveril]

Summary

• normalize every detected text file through Git attributes
• force LF endings in both the repository and working trees on every platform
• avoid cross-platform diffs and shell, Nix, YAML, TOML, or Rust parsing surprises after Windows checkouts

Validation

• git add --renormalize . produced no content-file changes
• git diff --check
• git ls-files --eol confirms text=auto eol=lf