[BUG] --include-hook-events flag not emitting hook lifecycle events to message stream

## Problem
When using the Claude Agent SDK (Python v0.2.87) with `include_hook_events=True`,
hook callbacks execute correctly but `hook_started` and `hook_response` system messages
are not emitted to the message stream, despite the `--include-hook-events` CLI flag
being passed to Claude Code.

## Expected Behavior
According to the [Agent SDK documentation](https://code.claude.com/docs/en/agent-sdk/hooks),
when `include_hook_events=True` is set, the CLI should emit hook lifecycle events
(`hook_started` and `hook_response` messages with `type: "system"` and `subtype` in
`["hook_started", "hook_response"]`) into the message stream as `HookEventMessage` objects.

## Actual Behavior
- Hook callbacks ARE returning correct `hookSpecificOutput` format
- `--include-hook-events` CLI flag IS being passed to Claude Code
- BUT `hook_started` and `hook_response` system messages NEVER appear in the stream
- Only `init` and `status` system messages appear

## Steps to Reproduce
1. Use Claude Agent SDK (Python) with `include_hook_events=True`
2. Register `PreToolUse` and `PostToolUse` hooks
3. Make a query that triggers tool use
4. Listen to message stream with `client.receive_messages()`
5. Observe that `HookEventMessage` objects never appear

## Environment
- Claude Code CLI: 2.1.150
- Claude Agent SDK (Python): 0.2.87
- Output format: stream-json
- Mode: Streaming/bidirectional

## Logs
Hook callbacks execute and print to console, confirming they're being called.
However, no `hook_started` or `hook_response` messages appear in the parsed message stream.

python api.py
INFO: Started server process [34419]
INFO: Waiting for application startup.
INFO: Application startup complete.
INFO: Uvicorn running on http://0.0.0.0:8000 (Press CTRL+C to quit)
INFO: 127.0.0.1:51645 - "GET /chat HTTP/1.1" 200 OK
****************************************************************************************************
PreToolUse Event:
{'session_id': 'a561c82a-f6d7-4c89-b6f3-f839625b5dd1', 'transcript_path': '/Users/raman/.claude/projects/-Users-raman-Developer-claude-agent-sdk-backend/a561c82a-f6d7-4c89-b6f3-f839625b5dd1.jsonl', 'cwd': '/Users/raman/Developer/claude-agent-sdk/backend', 'permission_mode': 'default', 'hook_event_name': 'PreToolUse', 'tool_name': 'Bash', 'tool_input': {'command': 'find . -type f ! -path "*/node_modules/*" ! -path "*/venv/*" | wc -l', 'description': 'Count files in current directory, excluding node_modules and venv'}, 'tool_use_id': 'toolu_019AASM8eM8emLZiY565mA7N'}
****************************************************************************************************
****************************************************************************************************
PostToolUse Event:
{'session_id': 'a561c82a-f6d7-4c89-b6f3-f839625b5dd1', 'transcript_path': '/Users/raman/.claude/projects/-Users-raman-Developer-claude-agent-sdk-backend/a561c82a-f6d7-4c89-b6f3-f839625b5dd1.jsonl', 'cwd': '/Users/raman/Developer/claude-agent-sdk/backend', 'permission_mode': 'default', 'hook_event_name': 'PostToolUse', 'tool_name': 'Bash', 'tool_input': {'command': 'find . -type f ! -path "*/node_modules/*" ! -path "*/venv/*" | wc -l', 'description': 'Count files in current directory, excluding node_modules and venv'}, 'tool_response': {'stdout': ' 3', 'stderr': '', 'interrupted': False, 'isImage': False, 'noOutputExpected': False}, 'tool_use_id': 'toolu_019AASM8eM8emLZiY565mA7N', 'duration_ms': 59}
****************************************************************************************************

##

[api.py](https://github.com/user-attachments/files/28233333/api.py)

SSE UI STREAMS LOGS
data: {"type": "system", "subtype": "init"}

data: {"type": "system", "subtype": "status"}

data: {"type": "thinking", "thinking": "The user wants to find the number of files in the current working directory, ignoring node_modules and venv folders.\n\nI should use the Bash tool to run a command that counts files while excluding those directories. A good approach would be to use `find` command with appropriate exclusion patterns.\n\nLet me run a command to count the files."}

data: {"type": "tool_use", "tool": "Bash", "input": {"command": "find . -type f ! -path \"*/node_modules/*\" ! -path \"*/venv/*\" | wc -l", "description": "Count files in current directory, excluding node_modules and venv"}}

data: {"type": "system", "subtype": "status"}

data: {"type": "thinking", "thinking": "The command found 3 files in the current working directory when excluding node_modules and venv directories."}

data: {"type": "text", "text": "There are **3 files** in the current working directory (excluding `node_modules` and `venv` directories)."}