fix(agent-loop): log tool/result under the originating call.id (P1-7)

The loop passed the authoritative call.id into ctx.tools.execute() but then
appended tool/result using result.callId — the value a tools/execute waterfall
listener returns — with no check. A listener returning a mismatched id silently
recorded the result under the wrong call. callId is the model-transcript
correlation id: deriveMessages() turns it into the tool-result block's
toolCallId, which must pair with the assistant tool-call block; a wrong id
orphans that pairing in the next model request.

Append tool/result with callId: call.id (the loop's authoritative id). A
listener-internal id, if ever worth keeping, belongs in a separate diagnostic
field — never overloaded onto callId.

Test: a tools/execute listener returns a wrong callId; assert the logged
tool/result.callId equals call.id AND deriveMessages() yields a tool-result
block whose toolCallId equals call.id (not the wrong returned id). Verified the
test fails on the pre-fix result.callId behavior.

packages/agent-loop/src/loop.ts

@@ -420,7 +420,13 @@ async function runStep(
     })
     session.append('tool/result', {
       turn, step,
-      callId: result.callId,
+      // The correlation id MUST be the loop's authoritative call.id (the
+      // model-transcript id that deriveMessages turns into toolCallId), NOT
+      // result.callId — a tools/execute waterfall listener returning a
+      // mismatched id would otherwise orphan the call↔result pairing in the
+      // next model request. A listener-internal id, if ever needed, belongs in
+      // a separate diagnostic field, never overloaded onto callId.
+      callId: call.id,
       content: result.content,
       isError: result.isError,
       ...result.error ? { error: result.error } : {},