feat: synthetic instruction generation via OpenRouter deepseek-v4-flash

tests/test_datagen.py

@@ -0,0 +1,16 @@
+from buddhagpt.datagen import build_messages, parse_pairs, dedupe
+
+def test_build_messages_varies_templates():
+    sutta = {"uid": "mn21", "title": "T", "text": "x" * 900}
+    prompts = {build_messages(sutta, v)[1]["content"] for v in range(6)}
+    assert len(prompts) == 6  # rotating templates, not one fixed prompt
+
+def test_parse_pairs_extracts_json_lines():
+    out = '{"question": "Q1?", "answer": "A1"}\n{"question": "Q2?", "answer": "A2"}'
+    assert len(parse_pairs(out, uid="mn21")) == 2
+
+def test_dedupe_drops_near_duplicates():
+    pairs = [{"question": "What is craving?", "answer": "a"},
+             {"question": "What is craving?", "answer": "b"},
+             {"question": "How does one practice metta?", "answer": "c"}]
+    assert len(dedupe(pairs)) == 2