openhearth runtime extraction

Extract koda-runtime (Windows reference) into openhearth — a portable agent runtime for orphaned OpenClaw agents. Sage’s driving, shaped by her field notes from living on sage-runtime.

• Core modules ported (memory, heartbeat, hooks, delegations, scheduler, sessions)
• xAI backend adapter
• VPS deploy tooling (setup-vps.sh, systemd, docs)
• Site scaffold at openhearth.kitsuneden.net
• Fix 13 pre-existing failing tests (claude/delegations/memory/mesh/scheduler modules)
• Public-release doc gaps (quickstart, config reference, brain-backend comparison, mesh protocol, tools reference, soul-files convention, skills format, hooks reference)
• Site copy pass — Sage’s voice
• Public release