Report actual inference smoke test destinations

docs/internal/generation.md

@@ -44,8 +44,10 @@ clients.
 The diagnostic path uses the same private attempt and retry implementation as
 ordinary generation. It retains invocation-local transport, response,
 generation, usage, capacity-wait, and retry-delay evidence before normal
-result-discard and cancellation checks. This evidence is returned to diagnostic
-orchestration; it is not added to public `ExecutionEvent` values or ordinary
+result-discard and cancellation checks. Built-in preparation also supplies its
+frozen request URL to the evidence path before attempts begin; injected
+generation has no equivalent HTTP destination. This evidence is returned to
+diagnostic orchestration; it is not added to public `ExecutionEvent` values or ordinary
 observer accounting. The [model-client document](llm.md) describes the
 transport-observation boundary, and the root
 [`SmokeTestReport` GoDoc](../../smoke_diagnostics.go) owns report semantics.