Directory name for plugin storage under the profile root.
Not an agent profile. The /agent picker reserves this name in addition to
requiring an AGENTS.md marker, so it is never listed as a selectable agent.
Defined here rather than in plugins.store because _reserved_names reads it
on the CLI startup path, and importing plugins.store pulls in the plugins
package __init__, which loads pydantic through plugins.models (see AGENTS.md
"Startup performance"). plugins.store re-exports it for its own callers.
