Add a variable for the Kotlin object member call receiver

Toward issue 1698: a call like MessageHelper.isRoomClosed() has
exactly two navigation segments, so the existing fully qualified
prefix capture (which only fires at three or more segments) never
sees it, and the code deliberately never stamps member_receiver for
this shape either, since that would defer the in file bare name
lookup that already resolves the same file case correctly.

This adds the new variable with no behavior change yet; capturing
into it and threading it through to raw_calls lands in the next
commits.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

graphify/extractors/engine.py

@@ -5846,6 +5846,7 @@ def _extract_generic(
             swift_receiver: str | None = None
             member_receiver: str | None = None
             kotlin_qualified_prefix: str | None = None
+            kotlin_object_receiver: str | None = None
             csharp_qualified_prefix: str | None = None
 
             # Special handling per language