Three-part fix for the top-level inline collapse bug:
1. plan-phase.md: add <runtime_compatibility> block after
</available_agent_types> that makes the Agent-availability
requirement explicit; workflow fails-closed (stops with a clear
log) in genuinely Agent-less contexts.
2. plan-phase.md: rename 7 "ORCHESTRATOR RULE — CODEX RUNTIME"
labels to "ALL RUNTIMES" so the spawn guard applies universally
(not just when Codex is detected).
3. execute-phase.md: scope the existing "Other runtimes" inline-
fallback prose to non-Claude contexts, preserving the #853
backgrounded-agent behaviour for Claude Code background agents.
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
(cherry picked from commit 5bf77a527f)
bb27263def