RemoteA2AAgent streaming mode mismatch with ClientConfig

[ankity]

Describe the Bug:
RemoteA2AAgent derives streaming mode from agentCard.capabilities().streaming(), but client execution path uses both clientConfig.isStreaming() and agentCard.capabilities().streaming().
This causes inconsistent mode decisions between layers when these values differ (e.g., card says streaming=true, client config says streaming=false), which can lead to send/stream flow mismatch and stuck completion behavior.

Steps to Reproduce:

1. Configure an A2A client with:
   • AgentCard capability streaming = true
   • ClientConfig streaming = false
2. Build remote agent via RemoteA2AAgent.builder(...).a2aClient(client).build().
3. Invoke remote agent in non-stream mode (message:send path).
4. Observe inconsistent behavior between remote agent mode assumptions and client transport mode (in our case, response returns but top-level reactive flow completion is inconsistent/hangs).

Expected Behavior:
A single effective streaming decision should be used consistently across RemoteA2AAgent and client transport.
If client config disables streaming, all layers should behave non-streaming.

Observed Behavior:
Mode decision is inconsistent:

• RemoteA2AAgent appears to use AgentCard capability only.
• Client transport path gates behavior with both client config and AgentCard capability.
  This mismatch can produce control-flow inconsistencies (including completion/hanging symptoms).

Environment Details:

• ADK Library Version (see maven dependency): 0.7.0
• OS: macOS

Model Information:

• Which model is being used: N/A / not model-specific (A2A transport+mode handling issue)

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Screenshots / Video:
N/A

Additional Context:
In our integration, client config explicitly disables streaming:

.clientConfig(ClientConfig.builder().setStreaming(false).build())

Even with this, behavior suggests another layer still treats streaming capability differently (derived from AgentCard).

Minimal Reproduction Code:

AgentCard agentCard = ... // capabilities.streaming() == true

Client client =
    Client.builder(agentCard)
        .withTransport(JSONRPCTransport.class, new JSONRPCTransportConfig(httpClient))
        .clientConfig(ClientConfig.builder().setStreaming(false).build())
        .build();

RemoteA2AAgent remote =
    RemoteA2AAgent.builder()
        .name(agentCard.name())
        .description(agentCard.description())
        .agentCard(agentCard)
        .a2aClient(client)
        .build();

// invoke non-stream operation (message:send)
// observe mismatch in mode behavior between remote agent and client transport

How often has this issue occurred?:

• Always (100%)