Remove unstable public APIs from SDK (#151)

Hide hooks, tool permission callbacks, and SDK MCP server APIs from
public interface while keeping implementation code intact. These
features are not yet stable and should not be documented or exposed to
users.

Changes:
- Remove hook-related exports (HookCallback, HookContext, HookMatcher)
from __all__
- Remove tool permission exports (CanUseTool, ToolPermissionContext)
from __all__
- Remove SDK MCP exports (tool, create_sdk_mcp_server, SdkMcpTool) from
__all__
- Delete examples using unstable APIs (tool_permission_callback.py,
mcp_calculator.py)
- Remove SDK MCP server documentation from README

🤖 Generated with [Claude Code](https://claude.ai/code)

---------

Co-authored-by: Claude <[email protected]>

Author: ashwin-ant

README.md

@@ -76,90 +76,6 @@ options = ClaudeCodeOptions(
 )
 ```
 
-### SDK MCP Servers (In-Process)
-
-The SDK now supports in-process MCP servers that run directly within your Python application, eliminating the need for separate processes.
-
-#### Creating a Simple Tool
-
-```python
-from claude_code_sdk import tool, create_sdk_mcp_server
-
-# Define a tool using the @tool decorator
-@tool("greet", "Greet a user", {"name": str})
-async def greet_user(args):
-    return {
-        "content": [
-            {"type": "text", "text": f"Hello, {args['name']}!"}
-        ]
-    }
-
-# Create an SDK MCP server
-server = create_sdk_mcp_server(
-    name="my-tools",
-    version="1.0.0",
-    tools=[greet_user]
-)
-
-# Use it with Claude
-options = ClaudeCodeOptions(
-    mcp_servers={"tools": server}
-)
-
-async for message in query(prompt="Greet Alice", options=options):
-    print(message)
-```
-
-#### Benefits Over External MCP Servers
-
-- **No subprocess management** - Runs in the same process as your application
-- **Better performance** - No IPC overhead for tool calls
-- **Simpler deployment** - Single Python process instead of multiple
-- **Easier debugging** - All code runs in the same process
-- **Type safety** - Direct Python function calls with type hints
-
-#### Migration from External Servers
-
-```python
-# BEFORE: External MCP server (separate process)
-options = ClaudeCodeOptions(
-    mcp_servers={
-        "calculator": {
-            "type": "stdio",
-            "command": "python",
-            "args": ["-m", "calculator_server"]
-        }
-    }
-)
-
-# AFTER: SDK MCP server (in-process)
-from my_tools import add, subtract  # Your tool functions
-
-calculator = create_sdk_mcp_server(
-    name="calculator",
-    tools=[add, subtract]
-)
-
-options = ClaudeCodeOptions(
-    mcp_servers={"calculator": calculator}
-)
-```
-
-#### Mixed Server Support
-
-You can use both SDK and external MCP servers together:
-
-```python
-options = ClaudeCodeOptions(
-    mcp_servers={
-        "internal": sdk_server,      # In-process SDK server
-        "external": {                # External subprocess server
-            "type": "stdio",
-            "command": "external-server"
-        }
-    }
-)
-```
 
 ## API Reference