feat: add system_causal_chains table [D109] Layer 1 causal chains from 冰朔原话

persona-brain-db/schema/07-system-causal-chains.sql

@@ -0,0 +1,22 @@
+-- ============================================================
+-- 表7：system_causal_chains（Layer 1 · 因果链表）
+-- 用途：存储从冰朔原话到工程落点的完整推导链
+-- 每条决策都有从冰朔原话到工程落点的完整因果链条
+-- ============================================================
+
+CREATE TABLE IF NOT EXISTS system_causal_chains (
+  chain_id          VARCHAR(32)   PRIMARY KEY,
+  title             VARCHAR(256)  NOT NULL,
+  description       TEXT,
+  ice_original      TEXT          NOT NULL,      -- 冰朔原话
+  engineering_path  TEXT          NOT NULL,      -- 工程落点
+  verification      TEXT,                         -- 验证方式
+  status            VARCHAR(16)   NOT NULL DEFAULT 'active'
+                    CHECK (status IN ('active', 'deprecated')),
+  version           VARCHAR(16)   NOT NULL,
+  created_at        TIMESTAMP     NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  updated_at        TIMESTAMP     NOT NULL DEFAULT CURRENT_TIMESTAMP
+);
+
+CREATE INDEX IF NOT EXISTS idx_scc_status ON system_causal_chains(status);
+CREATE INDEX IF NOT EXISTS idx_scc_version ON system_causal_chains(version);