Skills injecting into system prompt even with plugin disabled — consuming 22% context at session start

I have all plugins set to false in my settings.json, and all claude.ai Connectors are disconnected. Despite this, every new Claude Code session starts at 22-24% context usage before I type a single message.

According to the /usage stats, the "superpowers" plugin accounts for 11% of my usage, and its skills (brainstorming, writing-plans, subagent-driven-development) appear in the system prompt skills list at session start — even though the plugin is disabled.