[Feat]: A2A client to work as a router and route request to respective agent based on prompt (we can provide multiple agent cards to A2A client)

### Is your feature request related to a problem? Please describe.

Currently, when working with multiple A2A agents, developers need to build a separate router/orchestration agent to determine which agent should handle a user's request. This approach has several drawbacks:

**Additional Development Overhead:** Requires building and maintaining a dedicated routing agent with its own LLM calls, prompt engineering, and decision logic

**Performance Impact:** Adds an extra network hop and LLM inference call just for routing:

**Maintenance Burden:** The router agent needs to be updated whenever:

New agents are added
Agent capabilities change
Sample prompts evolve

### Describe the solution you'd like

Enhance the A2A Client SDK to support built-in intelligent routing by accepting multiple agent cards and automatically selecting the appropriate agent based on the user's prompt.

How It Works:
**Agent Card Metadata:** A2A client reads from each agent card:
**Smart Matching:** A2A client uses lightweight matching algorithm (keyword matching, in-memory embeddings) to score each agent card against the user prompt
**Automatic Routing**: Selects the best-match agent and forwards the request
**Fallback Mechanism:** If no clear match, return error or ask user to clarify
**Audit:** Log which agent was selected and why (routing metadata)

**Compatibility**
**Backward Compatible:** Existing single-agent usage continues to work
**Opt-in Feature:** Routing only enabled when multiple agents registered
**Graceful Degradation:** If routing fails, return error with suggestions

### Describe alternatives you've considered

- using our own embeddings to find which agent to route to.

### Additional context

_No response_

### Code of Conduct

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