Add voice roster validator for caller_gen

backend/services/caller_gen.py

@@ -36,3 +36,12 @@ def parse_batch_response(raw: str) -> list[CallerIdentity]:
             raise ValueError(f"CallerIdentity missing fields: {missing}")
         result.append(CallerIdentity(**{k: c[k] for k in REQUIRED_FIELDS}))
     return result
+
+
+def resolve_voice(suggestion: str, roster: list[str]) -> str:
+    """Map sonnet's voice suggestion to a real voice in the roster.
+    Case-insensitive exact match; deterministic fallback to first roster entry."""
+    if not suggestion or not roster:
+        return roster[0] if roster else ""
+    lower_map = {v.lower(): v for v in roster}
+    return lower_map.get(suggestion.lower(), roster[0])

tests/test_caller_gen.py

@@ -35,3 +35,27 @@ def test_parse_batch_response_rejects_missing_fields():
     bad = '{"callers": [{"name": "Jim"}]}'
     with pytest.raises(ValueError, match="missing"):
         parse_batch_response(bad)
+
+
+def test_resolve_voice_matches_exact():
+    from backend.services.caller_gen import resolve_voice
+    roster = ["Marcus", "Dennis", "Priya", "Edward"]
+    assert resolve_voice("Marcus", roster) == "Marcus"
+
+
+def test_resolve_voice_case_insensitive():
+    from backend.services.caller_gen import resolve_voice
+    roster = ["Marcus", "Dennis"]
+    assert resolve_voice("marcus", roster) == "Marcus"
+
+
+def test_resolve_voice_falls_back_when_no_match():
+    from backend.services.caller_gen import resolve_voice
+    roster = ["Marcus", "Dennis"]
+    # Deterministic fallback: return first from roster
+    assert resolve_voice("Santiago", roster) == "Marcus"
+
+
+def test_resolve_voice_empty_suggestion_falls_back():
+    from backend.services.caller_gen import resolve_voice
+    assert resolve_voice("", ["Marcus"]) == "Marcus"