fix(quick-dev): preserve source line endings in render.py

Python text-mode open() with the platform default performs universal-
newline translation: on Windows, LF source files get written as CRLF,
producing spurious diffs when rendered output is compared against
source. Pass newline="" on both the source read and the rendered
write so line endings pass through verbatim.

Part of plan-quick-dev-python-config-hardening.md (F4).

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

src/bmm-skills/4-implementation/bmad-quick-dev/render.py

@@ -137,9 +137,9 @@ def main():
             continue
         src = posixpath.join(script_dir, fname)
         dst = posixpath.join(out_dir, fname)
-        with open(src, "r", encoding="utf-8") as fh:
+        with open(src, "r", encoding="utf-8", newline="") as fh:
             content = fh.read()
-        with open(dst, "w", encoding="utf-8") as fh:
+        with open(dst, "w", encoding="utf-8", newline="") as fh:
             fh.write(render_template(content, vars_))
         count += 1