Refactor responses-backed Agent sessions (#281)

## Summary
- require explicit sessions when using the responses-backed
Agent/AsyncAgent and remove legacy AgentConfig plumbing
- add shared session-scoped tracking for streamed responses and update
ReActAgent wrapper
- extend unit/integration coverage for multi-session flows and combined
server/client tool streaming

## Testing
- uv run ruff check
- uv run pytest tests/lib/agents/test_agent_responses.py
- TEST_API_BASE_URL=http://127.0.0.1:8321
LLAMA_STACK_TEST_MODEL=ollama/llama3.2:3b-instruct-fp16 uv run pytest
tests/integration/test_agent_responses_e2e.py

Author: ashwinb

examples/README.md

@@ -0,0 +1,111 @@
+# Examples
+
+This directory contains example scripts and interactive tools for exploring the Llama Stack Client Python SDK.
+
+## Interactive Agent CLI
+
+`interactive_agent_cli.py` - An interactive command-line tool for exploring agent turn/step events with server-side tools.
+
+### Features
+
+- 🔍 **File Search Integration**: Automatically sets up a vector store with sample knowledge base
+- 📊 **Event Streaming**: See real-time turn/step events as the agent processes your queries
+- 🎯 **Server-Side Tools**: Demonstrates file_search and other server-side tool execution
+- 💬 **Interactive REPL**: Chat-style interface for easy exploration
+
+### Prerequisites
+
+1. Start a Llama Stack server with OpenAI provider:
+   ```bash
+   cd ~/local/llama-stack
+   source ../stack-venv/bin/activate
+   export OPENAI_API_KEY=<your-key>
+   llama stack run ci-tests --port 8321
+   ```
+
+2. Install the client (from repository root):
+   ```bash
+   cd /Users/ashwin/local/new-stainless/llama-stack-client-python
+   uv sync
+   ```
+
+### Usage
+
+Basic usage (uses defaults: openai/gpt-4o, localhost:8321):
+```bash
+cd examples
+uv run python interactive_agent_cli.py
+```
+
+With custom options:
+```bash
+uv run python interactive_agent_cli.py --model openai/gpt-4o-mini --base-url http://localhost:8321
+```
+
+### Example Session
+
+```
+╔══════════════════════════════════════════════════════════════╗
+║                                                              ║
+║        🤖  Interactive Agent Explorer  🔍                    ║
+║                                                              ║
+║  Explore agent turn/step events with server-side tools      ║
+║                                                              ║
+╚══════════════════════════════════════════════════════════════╝
+
+🔧 Configuration:
+  Model: openai/gpt-4o
+  Server: http://localhost:8321
+
+🔌 Connecting to server...
+  ✓ Connected
+
+📚 Setting up knowledge base...
+  Indexing documents....... ✓
+  Vector store ID: vs_abc123
+
+🤖 Creating agent with tools...
+  ✓ Agent ready
+
+💬 Type your questions (or 'quit' to exit, 'help' for suggestions)
+──────────────────────────────────────────────────────────────
+
+🧑 You: What is Project Phoenix?
+
+🤖 Assistant:
+
+  ┌─── Turn turn_abc123 started ───┐
+  │                                 │
+  │  🧠 Inference Step 0 started    │
+  │  🔍 Tool Execution Step 1       │
+  │     Tool: knowledge_search      │
+  │     Status: server_side         │
+  │  🧠 Inference Step 2            │
+  │  ✓ Response: Project Phoenix... │
+  │                                 │
+  └─── Turn completed ──────────────┘
+
+Project Phoenix is a next-generation distributed systems platform launched in 2024...
+```
+
+### What You'll See
+
+The tool uses `AgentEventLogger` to display:
+- **Turn lifecycle**: TurnStarted → TurnCompleted
+- **Inference steps**: When the model is thinking/generating text
+- **Tool execution steps**: When server-side tools (like file_search) are running
+- **Step metadata**: Whether tools are server-side or client-side
+- **Real-time streaming**: Text appears as it's generated
+
+### Sample Questions
+
+Type `help` in the interactive session to see suggested questions, or try:
+- "What is Project Phoenix?"
+- "Who is the lead architect?"
+- "What ports does the system use?"
+- "How long do JWT tokens last?"
+- "Where is the production environment deployed?"
+
+### Exit
+
+Type `quit`, `exit`, `q`, or press `Ctrl+C` to exit.