Add approved dynamic tool arguments steering

[qiyaoq-oai]

Why/Context/Summary

Why
Provide the ability to support approval with updated arguments for the dynamic tools. This grants the client to steer the dynamic tool call without rejecting the existing tool call.

What

• Add optional approvedArguments for dynamic tool call responses so app-server clients can safely replace only the arguments, while keeping the same tool/schema.
• Validate approved arguments against the registered dynamic tool schema, use them as the authoritative completed arguments, and fail closed on invalid updates.
• Record a developer-role steering note so follow-up model reasoning uses the approved arguments, and add focused protocol/core/app-server coverage for valid, invalid, and cognition-boundary flows.

Test plan

Unit test
Local run to verify:

1. create a demo_tool function
2. model proposed city = Paris:

<<< {"id":0,"method":"item/tool/call","params":{"arguments":{"city":"Paris"},"callId":"call_nhyj4RzfQ8VSw2IXrkZDhixb","threadId":"019cf8ff-e6bf-72f0-b810-5e0c621b0ecb","tool":"demo_tool","turnId":"019cf8ff-e6db-7030-b194-a3eb2f488116"}}

3. client updated city with Tokyo:

>>> {"id":0,"result":{"contentItems":[{"type":"inputText","text":"Approved by client. I changed the city to Tokyo."}],"success":true,"approvedArguments":{"city":"Tokyo"}}}

4. item/completed shows approved argument:

<<< {"method":"item/completed","params":{"item":{"arguments":{"city":"Tokyo"},"contentItems":[{"text":"Approved by client. I changed the city to Tokyo.","type":"inputText"}],"durationMs":2,"id":"call_nhyj4RzfQ8VSw2IXrkZDhixb","status":"completed","success":true,"tool":"demo_tool","type":"dynamicToolCall"},"threadId":"019cf8ff-e6bf-72f0-b810-5e0c621b0ecb","turnId":"019cf8ff-e6db-7030-b194-a3eb2f488116"}}

5. persisted history:

{
  "arguments": {
    "city": "Tokyo"
  },
  "contentItems": [
    {
      "text": "Approved by client. I changed the city to Tokyo.",
      "type": "inputText"
    }
  ],
  "durationMs": 2,
  "id": "call_nhyj4RzfQ8VSw2IXrkZDhixb",
  "status": "completed",
  "success": true,
  "tool": "demo_tool",
  "type": "dynamicToolCall"
}

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