Feature Request: Add session title to status line JSON input

Feature Request

Summary: Add the session title/name to the status line JSON input so it can be displayed in custom status lines.

Use Case

When using the /resume command, sessions are listed with their human-readable titles. Users who customize their status line would like to display this session title to easily identify which conversation they're working in.

Current Behavior

The status line command receives JSON with these fields:

• session_id (not human-readable)
• transcript_path
• cwd, model, context_window, cost, etc.

The session title shown in /resume is not included.

Requested Behavior

Add a field like session_title or session_name to the status line JSON input containing the human-readable session title.

Example:

{
  "session_id": "abc123...",
  "session_title": "My conversation about feature X",
  ...
}

This would allow users to display the session title in their custom status lines.

Additional Context

This came up while trying to add the session name to a custom status line script. The workaround of parsing transcript_path filename doesn't work because the title isn't stored there.