chore: check out LF line endings everywhere

The repository normalises to LF in the index either way; the working tree was
being converted to CRLF on checkout, which is wrong for a repo worked on from
Linux. It also silently breaks the newsletter parity suite, which compares
committed golden files byte for byte against engine stdout — the reason
scripts/newsletter needed an explicit LF override until now. That override and
the *.sh one are both redundant against an LF default.

.gitattributes

@@ -1,7 +1 @@
-* text=auto eol=crlf
-
-*.sh text eol=lf
-
-# The newsletter parity suite compares engine stdout to committed golden files
-# byte for byte, so these must stay LF on every checkout.
-scripts/newsletter/** text eol=lf
+* text=auto eol=lf