chore: add .gitattributes to normalize line endings to LF

Prevents cross-platform CRLF/LF churn between Windows and macOS checkouts.
Windows-only scripts (bat/cmd/ps1) pinned to CRLF; shell scripts pinned to LF.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitattributes

@@ -0,0 +1,30 @@
+# Normalize line endings on commit; check out LF on every OS.
+* text=auto eol=lf
+
+# Binary files — never touch line endings.
+*.png binary
+*.jpg binary
+*.jpeg binary
+*.gif binary
+*.ico binary
+*.webp binary
+*.pdf binary
+*.zip binary
+*.gz binary
+*.tar binary
+*.woff binary
+*.woff2 binary
+*.ttf binary
+*.otf binary
+*.eot binary
+*.mp4 binary
+*.mov binary
+*.wasm binary
+
+# Shell scripts must stay LF regardless.
+*.sh text eol=lf
+
+# Windows batch / PowerShell must stay CRLF.
+*.bat text eol=crlf
+*.cmd text eol=crlf
+*.ps1 text eol=crlf