chore: pin .cs line endings to LF for deterministic formatting

dotnet format has no end_of_line setting in .editorconfig, so it fell
back to the OS default (CRLF on Windows, LF on Linux). Combined with
.gitattributes '*.cs text' (native eol on checkout), local 'dotnet
format --verify' results depended on each contributor's core.autocrlf,
producing spurious whitespace failures on autocrlf=input machines while
CI (Windows, autocrlf=true) stayed green.

Pin .cs to LF in both .editorconfig (end_of_line = lf) and .gitattributes
(*.cs text eol=lf) so formatting is deterministic on every platform.
Blobs are already LF, so this is a no-op for file content.

Author: RandomCrocodile

.editorconfig

@@ -19,6 +19,7 @@ indent_size = 4
 indent_style = space
 
 [*.{cs,vb}]
+end_of_line = lf
 dotnet_separate_import_directive_groups = false
 dotnet_sort_system_directives_first = true
 dotnet_style_coalesce_expression = true:suggestion

.gitattributes

@@ -4,7 +4,7 @@
 # Explicitly declare text files we want to always be normalized and converted
 # to native line endings on checkout.
 *.config text
-*.cs text diff=csharp
+*.cs text eol=lf diff=csharp
 *.manifest text
 *.md text
 *.resx text