Store all text files with LF line endings

Some files had been saved with CRLF on Windows, so a one-line change
showed as a whole-file diff. .gitattributes now stores text as LF
(.bat stays CRLF for cmd, .command/.sh LF for macOS).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitattributes

@@ -1,4 +1,6 @@
+* text=auto eol=lf
 *.command text eol=lf
 *.sh text eol=lf
 *.bat text eol=crlf
 *.bin binary
+*.png binary