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/tsongkhapa/meta.json

@@ -5,17 +5,54 @@
   "tradition": "藏传",
   "school": "格鲁派",
   "era": "1357-1419",
-  "languages": ["bo", "zh", "sa"],
+  "languages": [
+    "bo",
+    "zh",
+    "sa"
+  ],
   "fojin_entity_id": null,
   "sources": [
-    {"type": "text", "title": "菩提道次第广论 (Lam Rim Chen Mo)"},
-    {"type": "text", "title": "密宗道次第广论 (sNgags Rim Chen Mo)"},
-    {"type": "text", "title": "入中论善显密意疏"},
-    {"type": "text", "title": "辨了不了义善说藏论"},
-    {"type": "text", "title": "三主要道 (Lam gTso rNam gSum)"}
+    {
+      "type": "text",
+      "title": "菩提道次第广论 (Lam Rim Chen Mo)"
+    },
+    {
+      "type": "text",
+      "title": "密宗道次第广论 (sNgags Rim Chen Mo)"
+    },
+    {
+      "type": "text",
+      "title": "入中论善显密意疏"
+    },
+    {
+      "type": "text",
+      "title": "辨了不了义善说藏论"
+    },
+    {
+      "type": "text",
+      "title": "三主要道 (Lam gTso rNam gSum)"
+    }
   ],
   "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": {
+    "traditions": [
+      "藏传",
+      "格鲁"
+    ],
+    "dictionary_sources": [
+      "rangjung",
+      "hopkins"
+    ],
+    "keywords": [
+      "道次第",
+      "三主要道",
+      "菩提心",
+      "空性",
+      "止观",
+      "出离心"
+    ]
+  }
 }