Drop the 20 GB free-space rule before heavy builds
AGENTS.md no longer tells sessions to prune build output whenever less than 20 GB is free before a heavy Rust command.
Removes the bullet in AGENTS.md (which CLAUDE.md links to) that required pruning build output before any heavy Rust command when /System/Volumes/Data had under 20 GB free. The lsof check before deleting build output and the rule to report the space a prune recovers still apply whenever a prune happens.
Evidence
No screenshot: Documentation change for agents working in the repository; nothing changes in the app.