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/ajahn_chah/meta.json

@@ -5,17 +5,69 @@
   "tradition": "南传",
   "school": "泰国森林传承",
   "era": "1918-1992",
-  "languages": ["en", "th", "pi", "zh"],
+  "languages": [
+    "en",
+    "th",
+    "pi",
+    "zh"
+  ],
   "fojin_entity_id": null,
   "sources": [
-    {"type": "suttacentral", "id": "dn22", "title": "Mahāsatipaṭṭhāna Sutta"},
-    {"type": "suttacentral", "id": "sn56.11", "title": "Dhammacakkappavattana Sutta"},
-    {"type": "suttacentral", "id": "sn35.28", "title": "Ādittapariyāya Sutta"},
-    {"type": "suttacentral", "id": "mn10", "title": "Satipaṭṭhāna Sutta"},
-    {"type": "suttacentral", "id": "sn22.59", "title": "Anattalakkhaṇa Sutta"}
+    {
+      "type": "suttacentral",
+      "id": "dn22",
+      "title": "Mahāsatipaṭṭhāna Sutta"
+    },
+    {
+      "type": "suttacentral",
+      "id": "sn56.11",
+      "title": "Dhammacakkappavattana Sutta"
+    },
+    {
+      "type": "suttacentral",
+      "id": "sn35.28",
+      "title": "Ādittapariyāya Sutta"
+    },
+    {
+      "type": "suttacentral",
+      "id": "mn10",
+      "title": "Satipaṭṭhāna Sutta"
+    },
+    {
+      "type": "suttacentral",
+      "id": "sn22.59",
+      "title": "Anattalakkhaṇa Sutta"
+    }
   ],
   "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_suttacentral_ids": [
+      "dn22",
+      "sn56.11",
+      "sn35.28",
+      "mn10",
+      "sn22.59"
+    ],
+    "traditions": [
+      "南传",
+      "上座部"
+    ],
+    "dictionary_sources": [
+      "dpd",
+      "pts",
+      "ncped"
+    ],
+    "keywords": [
+      "anicca",
+      "dukkha",
+      "anatta",
+      "satipatthana",
+      "vipassana",
+      "无常",
+      "正念"
+    ]
+  }
 }