gate: the rebuke turn is not a ground — second examination uses the caller's sources

The live round trip showed the second examination listing the gate's own
rebuke as source user_2. The rebuke is the gate's turn, not something the
caller gave the model; the second reply is now examined against the
caller's original body (same sources and query as the first). Test pins
it. Elixir gate 15/0.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

vav_pipeline/lib/vav_pipeline/gate.ex

@@ -47,7 +47,9 @@ defmodule VavPipeline.Gate do
 
           with :ok <- gather_call(),
                {:ok, 200, reply2} <- forward.(upstream, body2, key, extra),
-               {:ok, second} <- examine(upstream, body2, reply2, Keyword.put(examine_opts, :rebukes, first.bedikah_ref)) do
+               # Examined against what the CALLER gave (body, not body2): the
+               # rebuke is the gate's own turn and is not a ground.
+               {:ok, second} <- examine(upstream, body, reply2, Keyword.put(examine_opts, :rebukes, first.bedikah_ref)) do
             {:ok, deliver(upstream, reply2, second, first)}
           else
             {:ok, status, other} -> {:ok, %{status: status, reply: other, bedikah: nil, first: first, shorashim: nil}}