test(acp-example): re-record snapshot goldens after merging master

Master's "fix(acp): align prompt and workspace contracts" changed the editor-
facing transcript — `user/message` → `user_message_chunk` is now emitted during
session/load replay ONLY, not live streaming, so a live prompt no longer echoes
the user message back. The snapshot tier caught this (6 goldens shifted); this
re-records the four recorded scenarios against the API and re-accepts the two
authored goldens so they reflect the merged behavior. Full suite green and
deterministic; this is the tier working as designed.

examples/acp-agent/tests/snapshots/error-finish/stdout.golden.jsonl

@@ -1,4 +1,3 @@
 {"jsonrpc":"2.0","id":1,"result":{"protocolVersion":1,"agentInfo":{"name":"deepseek-harness-acp","version":"0.0.1"},"agentCapabilities":{"loadSession":true,"promptCapabilities":{"image":false,"audio":false,"embeddedContext":false}},"authMethods":[]}}
 {"jsonrpc":"2.0","id":2,"result":{"sessionId":"{{sessionId}}"}}
-{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"{{sessionId}}","update":{"sessionUpdate":"user_message_chunk","content":{"type":"text","text":"This prompt triggers a recorded provider error."}}}}
 {"jsonrpc":"2.0","id":3,"error":{"code":-32603,"message":"Internal error: turn failed: simulated provider error (HTTP 401)"}}