claude is already provided via tools.s (and the default tools include
s now), so drop the explicit claude entry and add s for direct access.

Use the new wrapper plugins option to install the GouvernAI plugin from
GitHub, providing the /guardrails command and gouvernai flow-state skill.

Allow declaratively adding extra Claude Code plugin directories alongside
the bundled one. Each entry becomes a repeatable --plugin-dir flag.

Add MegolmEvent callback that warns the user when a message can't be
decrypted and requests the missing room key. Also process invited_rooms
from the initial sync so invites that arrived while the bot was offline
are accepted instead of being silently ignored.