One-line definitions (`def a(x), do: b(x)`) have no do_block node: the
body is the value of the `do:` pair in the arguments keywords node. The
extractor only registered do_block bodies for the call-walk pass, so every
call inside a keyword-form body was silently dropped from the graph. When
there is no do_block, take the `do:` pair value as the body and walk it
the same way (Fixes#4207).
AI assistance: implementation drafted with Muse (Anthropic), reviewed and
verified by the author.
Signed-off-by: Raphael Malikian <rtmalikian@gmail.com>
(cherry picked from commit b00d3704db)
