Add Phase 8.2 CausalGraph wiki page and sidebar link - Phase-8-Causal-Graph.md (89th wiki page): CausalEdge/CausalNode/CausalGraphSnapshot dataclasses, CausalGraph DAG (thread-safe, OrderedDict LRU/FIFO eviction, DFS cycle detection, Kahn topological sort, DP critical path, to_dot/to_json/snapshot), CausalGraphBuilder (Jaccard contributor overlap, window_ms, min_weight, edge_strategy), build_causal_graph() factory, CognitiveCycle integration, 5 Prometheus metrics + PromQL, 12 test targets, 14-step impl order, Phase 8 roadmap table - _Sidebar.md: Phase 8 section now 2 links — Causal Graph added