test: normalize CRLF in the windows.ps1 handoff guard reader

.gitattributes forces eol=crlf for *.ps1, so CI checkouts hand the test
CRLF content and the SelfTest-strip regex anchors never matched; it went
unnoticed while the stripped fixture blocks contained no offenders.

tests/test_desktop_update_windows_python_handoff.py

@@ -37,7 +37,10 @@ WINDOWS_PS1 = REPO_ROOT / "scripts" / "desktop-update" / "windows.ps1"
 
 
 def _read() -> str:
-    return WINDOWS_PS1.read_text(encoding="utf-8")
+    # windows.ps1 is eol=crlf in .gitattributes, so checkouts materialize
+    # CRLF on disk (CI included). Normalize so the SelfTest-block strip's
+    # `\n}\n` anchors match regardless of the working-copy line endings.
+    return WINDOWS_PS1.read_text(encoding="utf-8").replace("\r\n", "\n")
 
 
 def _handoff_source() -> str: