fix: Anthropic responses with multiple text blocks lose all but the first (#1255)

* fix: concatenate all Anthropic text blocks, not just the first

* test: Anthropic response parsing concatenates text blocks

tests/test_anthropic_response_parse.py

@@ -0,0 +1,27 @@
+"""Tests for _parse_anthropic_response (src/llm_core.py)."""
+
+from src.llm_core import _parse_anthropic_response
+
+
+def test_concatenates_multiple_text_blocks():
+    # Regression: only the first text block was returned, dropping the rest.
+    data = {"content": [
+        {"type": "text", "text": "Part A "},
+        {"type": "tool_use", "id": "t1", "name": "x", "input": {}},
+        {"type": "text", "text": "Part B"},
+    ]}
+    assert _parse_anthropic_response(data) == "Part A Part B"
+
+
+def test_skips_non_text_blocks():
+    data = {"content": [
+        {"type": "thinking", "thinking": "..."},
+        {"type": "text", "text": "answer"},
+    ]}
+    assert _parse_anthropic_response(data) == "answer"
+
+
+def test_single_block_and_empty():
+    assert _parse_anthropic_response({"content": [{"type": "text", "text": "hi"}]}) == "hi"
+    assert _parse_anthropic_response({"content": []}) == ""
+    assert _parse_anthropic_response({}) == ""