chore: pin line endings to LF via .gitattributes

The repo already stores every text file as LF in the index, but Windows
clones with global core.autocrlf=true rewrite the working tree to CRLF
on checkout. Subsequent edits made through tooling that writes LF (most
editors and AI agents do) trigger 'LF will be replaced by CRLF the next
time Git touches it' warnings on every commit.

Pinning eol=lf in .gitattributes overrides the contributor's global
autocrlf setting for this repo and silences the warning. PowerShell on
Windows handles LF fine, and the devcontainer already runs Linux.

NOTE: GitHub template repos are one-time copies at creation, so this
fix does NOT propagate to repositories already created from this
template. Existing downstream repos must apply the same .gitattributes
change separately.

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

Author: tablackburn

.gitattributes

@@ -1,2 +1,10 @@
+# Normalize line endings to LF in both the repo and the working tree, regardless of
+# the contributor's global core.autocrlf setting. PowerShell on Windows handles LF
+# fine, and the devcontainer runs Linux. Without this, Windows clones with
+# core.autocrlf=true emit "LF will be replaced by CRLF the next time Git touches it"
+# warnings on every commit when files are edited by tooling that writes LF (most
+# editors and AI agents do).
+* text=auto eol=lf
+
 # The docs are generated by the build script and should be considered artifacts
 docs/en-US/* linguist-generated