SessionStart: query OpenBrain for recent activity + project context,
inject into Claude's context window on every new session.
Stop: async save session context to OpenBrain when git changes exist.
PreCompact: save working state to OpenBrain before context compaction.
API key read from ~/.claude/brain.key or CORE_BRAIN_KEY env var.
Co-Authored-By: Virgil <virgil@lethean.io>
