fix(quarto-citeproc): pin CSL lockfile and manifest to LF line endings

csl_validate_manifest byte-compares tests/csl_conformance.lock against a
generated LF-only string. With core.autocrlf=true and no .gitattributes,
Windows checkouts get CRLF for that file, producing a false "Lockfile
mismatch" unrelated to any real enabled_tests.txt/fixture divergence.

Pins tests/csl_conformance.lock and tests/enabled_tests.txt to eol=lf,
same pattern crates/pampa/.gitattributes already uses for its fixtures.
eol=lf overrides core.autocrlf for these paths in both directions, so
regenerating the lockfile from Windows stays safe too.

Author: cderv

crates/quarto-citeproc/.gitattributes

@@ -0,0 +1,7 @@
+# The CSL conformance manifest lockfile is byte-compared against a
+# generated LF-only string in tests/integration/csl_conformance.rs
+# (build_lockfile()). Without this pin, core.autocrlf=true checks the
+# file out as CRLF on Windows, producing a false "Lockfile mismatch"
+# unrelated to any real enabled_tests.txt/fixture divergence.
+tests/csl_conformance.lock text eol=lf
+tests/enabled_tests.txt text eol=lf