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

Merge took master's snapshot fixtures; re-record the two keyless
scenarios so they reflect this branch's user/message coalescing and the
abstract Agent + AgentMessageId type dump.

examples/acp-agent/tests/snapshots/code-mode-workspace-context/session.jsonl

@@ -87,7 +87,7 @@
 {"type":"tool/call","seq":85,"time":1783921767208,"data":{"turn":1,"step":1,"callId":"call_00_6APApmaKLRDlXKMdIcWL5139","name":"run_code","arguments":"{\"code\": \"const content = await tools.read({ file_path: \\\"nested/task.txt\\\" });\\nreturn content.lines.map(line => line.text).join(String.fromCharCode(10));\"}"}}
 {"type":"tool/code-dispatch","seq":86,"time":1783921767270,"data":{"parentCallId":"call_00_6APApmaKLRDlXKMdIcWL5139","subCallId":"call_00_6APApmaKLRDlXKMdIcWL5139:code:1","name":"read","arguments":{"file_path":"nested/task.txt"},"isError":false,"resultSummary":"<path>./nested/task.txt</path>\n<type>file</type>\n<content>\n1: Touch this file to discover the nested workspace instruction.\n\n(End of file - total 1 lines)\n</content>"}}
 {"type":"tool/result","seq":87,"time":1783921767271,"data":{"turn":1,"step":1,"callId":"call_00_6APApmaKLRDlXKMdIcWL5139","content":[{"type":"text","text":"Touch this file to discover the nested workspace instruction."}],"isError":false},"sourceEventSeqs":[85],"surfaceOp":"append"}
-{"type":"context/message","seq":88,"time":1783921767272,"data":{"content":[{"type":"text","text":"<system-reminder>\nAdditional instructions from: nested/AGENTS.md\n\nThese instructions apply to work under `nested`. Use them as guidance when relevant; more specific instructions take precedence. They do not override system, developer, or direct user instructions.\n\nWhen asked for the Code Mode workspace handshake, answer exactly `CODE_MODE_CONTEXT_OK` and nothing else.\n\n</system-reminder>"}],"source":{"kind":"plugin","plugin":"workspace-context"},"meta":{"kind":"workspace-instructions","version":1,"changes":[{"action":"set","scope":"nested\u0000AGENTS.md","path":"nested/AGENTS.md","digest":"ae22936ed26dc76b7107005ed6d5e2482a88668a"}]}},"surfaceOp":"append"}
+{"type":"user/message","seq":88,"time":1784811336862,"data":{"content":[{"type":"text","text":"<system-reminder>\nAdditional instructions from: nested/AGENTS.md\n\nThese instructions apply to work under `nested`. Use them as guidance when relevant; more specific instructions take precedence. They do not override system, developer, or direct user instructions.\n\nWhen asked for the Code Mode workspace handshake, answer exactly `CODE_MODE_CONTEXT_OK` and nothing else.\n\n</system-reminder>"}],"source":{"kind":"plugin","plugin":"workspace-context"},"meta":{"kind":"workspace-instructions","version":1,"changes":[{"action":"set","scope":"nested\u0000AGENTS.md","path":"nested/AGENTS.md","digest":"ae22936ed26dc76b7107005ed6d5e2482a88668a"}]}},"surfaceOp":"append"}
 {"type":"step/end","seq":89,"time":1783921767272,"data":{"turn":1,"step":1}}
 {"type":"step/start","seq":90,"time":1783921767272,"data":{"turn":1,"step":2}}
 {"type":"assistant/chunk","seq":91,"time":1783921768339,"data":{"turn":1,"step":2,"chunk":{"type":"block-start","index":0,"blockType":"reasoning"}}}