Clarify documentation on subagent loading behavior (manual file creation vs. `/agents` command)

Title: Clarify documentation on subagent loading behavior (manual file creation vs. /agents command)

Labels: documentation, enhancement

Body:

Hello Claude Code Team,

First off, thank you for building such a powerful and flexible tool. The custom subagents feature is fantastic.

I've identified a small area in the documentation that could be clarified to prevent user confusion regarding how and when custom subagents are loaded.

The Issue

Currently, the documentation describes two ways to create custom subagents:

1. Using the /agents command: The documentation in en/docs/claude-code/sub-agents under the "Quick start" section explicitly states that after creation, "Your subagent is now available!". This clearly indicates the agent is loaded immediately within the active session.

1. Manually creating a .md file: The documentation in the same file, under "Managing subagents" -> "Direct file management," shows how to create the agent file using mkdir and echo. However, it does not specify when an agent created this way becomes available.

My assumption, based on how most CLI tools handle configuration, is that a manually created file will only be loaded after restarting Claude Code. However, the documentation doesn't explicitly confirm this.

Why This Matters

This ambiguity can lead to a confusing user experience. A user might:

1. Read the documentation and manually create a .claude/agents/my-agent.md file.
2. Try to invoke @my-agent or expect it to be used automatically in the same session.
3. Conclude that the feature is broken or they configured it incorrectly when it doesn't work.
4. Spend unnecessary time troubleshooting, when a simple restart is all that's needed.

Proposed Solution

I suggest adding a brief, explicit note to the "Direct file management" section to clarify this behavior.

A simple addition like this would be perfect:

Note: Subagents created by manually adding files will be loaded the next time you start a Claude Code session. To create and use a subagent immediately without restarting, please use the /agents command.

This small clarification would set clear expectations for users and directly contrast the two methods, highlighting the convenience of the /agents command while explaining the behavior of the manual method.

Affected Documentation

• File: en/docs/claude-code/sub-agents.md
• Sections: Primarily the "Direct file management" section, but the context comes from the "Quick start" section.

Thank you for your consideration and for your excellent work on this project