The T3 subagent override spawns pi with --no-extensions, which silently
cost users every other extension they had installed. Re-discover the
user's extensions (agent dir, plus project .pi/extensions only under
standing trust) and re-add them with explicit --extension flags. Child
subagent spawns now also attach the T3 MCP extension so t3_thread_*
tools survive the nested spawn.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>