Vendor the 43 ce-* persona definitions (from compound-engineering 3.9.4),
add installBundledCeAgents() mirroring the skill installer (pinned,
plugin-local, idempotent, never a global ~/.claude/agents), install them
in onLoad, and expose the install dir to executor/step sessions via an
executorRuntimeEnv hook (FUSION_CE_AGENTS_DIR).
Together with U2's systemPromptOverride this gives the lightweight
subagent path: a CE skill reads a persona def from FUSION_CE_AGENTS_DIR
and passes its body to fn_spawn_agent. Installer test added (19 plugin
tests green).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>