Add infrastructure.world.hardening module with:
- MultiClientStressRunner: run 6+ concurrent automated clients via
asyncio.gather, meeting the Phase 8 multi-player stability target
- QuestArbiter: first-come-first-served quest-state locking to resolve
conflicts when multiple agents advance the same quest simultaneously
- AntiGriefPolicy: sliding-window rate limiter + blocked-action set
(destroy, kill_npc, steal, grief, cheat, spawn_item) for community
agent deployments
- RecoveryManager: periodic JSONL snapshots of adapter state with
restore-by-id or latest-snapshot recovery on restart
- WorldStateBackup: timestamped JSON backup files with manifest and
configurable rotation (max_backups=10 default)
- ResourceMonitor: CPU/RAM/disk sampling via psutil (when available)
with stdlib fallback; peak_cpu/peak_memory helpers for load reports
61 tests added covering all six components.
Fixes#860
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
