feat: add search_scope to all teachers + cross-reference tool for inter-teacher dialogue

Each teacher's meta.json now includes search_scope with tradition-specific
CBETA/SuttaCentral IDs, dictionary sources, and keywords for focused RAG
retrieval. New tools/cross_reference.py enables lineage queries and
cross-tradition concept comparison via FoJin KG.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

prebuilt/yinguang/meta.json

@@ -4,18 +4,70 @@
   "tradition": "汉传",
   "school": "净土宗",
   "era": "1861-1940",
-  "languages": ["zh-classical", "zh"],
+  "languages": [
+    "zh-classical",
+    "zh"
+  ],
   "fojin_entity_id": null,
   "sources": [
-    {"type": "cbeta", "id": "X62n1182", "title": "印光法师文钞正编"},
-    {"type": "cbeta", "id": "X62n1183", "title": "印光法师文钞续编"},
-    {"type": "cbeta", "id": "X62n1184", "title": "印光法师文钞三编"},
-    {"type": "cbeta", "id": "T12n0366", "title": "佛说阿弥陀经"},
-    {"type": "cbeta", "id": "T12n0365", "title": "佛说观无量寿佛经"},
-    {"type": "cbeta", "id": "T12n0360", "title": "佛说无量寿经"}
+    {
+      "type": "cbeta",
+      "id": "X62n1182",
+      "title": "印光法师文钞正编"
+    },
+    {
+      "type": "cbeta",
+      "id": "X62n1183",
+      "title": "印光法师文钞续编"
+    },
+    {
+      "type": "cbeta",
+      "id": "X62n1184",
+      "title": "印光法师文钞三编"
+    },
+    {
+      "type": "cbeta",
+      "id": "T12n0366",
+      "title": "佛说阿弥陀经"
+    },
+    {
+      "type": "cbeta",
+      "id": "T12n0365",
+      "title": "佛说观无量寿佛经"
+    },
+    {
+      "type": "cbeta",
+      "id": "T12n0360",
+      "title": "佛说无量寿经"
+    }
   ],
   "version": "1.0.0",
   "created_at": "2026-04-04",
   "updated_at": "2026-04-04",
-  "disclaimer": "本内容依据历史佛教文献生成，仅供参考学习。如需正式修行指导，请亲近善知识。"
+  "disclaimer": "本内容依据历史佛教文献生成，仅供参考学习。如需正式修行指导，请亲近善知识。",
+  "search_scope": {
+    "primary_cbeta_ids": [
+      "X62n1182",
+      "X62n1183",
+      "X62n1184",
+      "T12n0366",
+      "T12n0365",
+      "T12n0360"
+    ],
+    "traditions": [
+      "净土"
+    ],
+    "dictionary_sources": [
+      "foguang",
+      "dingfubao"
+    ],
+    "keywords": [
+      "念佛",
+      "净土",
+      "往生",
+      "信愿行",
+      "阿弥陀",
+      "极乐"
+    ]
+  }
 }