feat: add dynamic permission mode and model switching to ClaudeSDKClient

[dicksontsai]

Summary

• Adds set_permission_mode() method to dynamically change permission modes during streaming sessions
• Adds set_model() method to switch AI models mid-conversation
• Implements control protocol support matching the TypeScript SDK's capabilities

Motivation

The TypeScript SDK supports dynamic control through setPermissionMode() and setModel() methods on the Query interface. This PR brings the same functionality to the Python SDK, allowing users to:

1. Start with restrictive permissions for code review, then switch to acceptEdits for implementation
2. Use different models for different parts of a task (e.g., Sonnet for complex analysis, Haiku for simple tasks)
3. Adjust permissions based on workflow needs without restarting sessions

Changes

• ClaudeSDKClient: Added set_permission_mode(mode) and set_model(model) methods
• Internal Query class: Added set_model(model) method to send control requests
• E2E tests: Added comprehensive tests verifying the functionality works with real API calls

Test Plan

• All existing unit tests pass (102 tests)
• New E2E tests added and passing:
  • test_set_permission_mode: Verifies permission mode changes take effect
  • test_set_model: Confirms model switching works mid-conversation
  • test_interrupt: Validates interrupt capability
• Type checking passes (mypy)
• Linting passes (ruff)

Usage Example

async with ClaudeSDKClient() as client:
    # Start with default permissions for review
    await client.query("Analyze this code for issues")
    
    # Switch to auto-accept edits for implementation
    await client.set_permission_mode('acceptEdits')
    await client.query("Now fix the issues we found")
    
    # Use a different model for simpler tasks
    await client.set_model('claude-3-5-haiku-20241022')
    await client.query("Add a simple docstring")

🤖 Generated with Claude Code