test(e2e): delay the draft-proof final answer past the start gate

A progress draft only exists while the agent is working, and OpenClaw's exec
returns instantly for a mock tool call, so the whole turn finished in ~86ms —
inside the 1.5s draft gate. No draft was created, which is correct behavior but
proves nothing about rendering.

The draft-proof scenario now holds its final answer (MOCK_DRAFTPROOF_FINAL_DELAY_MS,
default 6s) so the turn straddles the gate. That is what made the live Discord
recording possible: draft created, edited with the status headline above the
tool line, replaced by the final answer, then deleted.

scripts/e2e/mock-openai-server.mjs

@@ -600,6 +600,10 @@ const server = http.createServer((req, res) => {
           );
           return;
         }
+        // Hold the final answer so the turn outlives the progress-draft start
+        // gate. Without this the whole turn finishes in well under a second and
+        // no draft is created, which is correct behavior but proves nothing.
+        await delay(readPositiveIntEnv("MOCK_DRAFTPROOF_FINAL_DELAY_MS", 6000));
         writeChatCompletion(res, body.stream !== false, "OPENCLAW_E2E_DRAFTPROOF");
         return;
       }