feat(fusion): add disease/modality weight registry

src/fusion/weights.py

@@ -0,0 +1,48 @@
+"""Disease × modality weight registry for the fusion engine.
+
+Heuristic preset weights — tune offline as clinician feedback arrives.
+"""
+from __future__ import annotations
+
+from typing import Mapping
+
+DEFAULT_WEIGHTS: dict[str, dict[str, float]] = {
+    "alzheimers": {
+        "mri":             0.35,
+        "eeg":             0.20,
+        "clinical_mmse":   0.20,
+        "clinical_moca":   0.15,
+        "clinical_age":    0.10,
+    },
+    "parkinsons": {
+        "mri":             0.20,
+        "eeg":             0.30,
+        "clinical_updrs":  0.30,
+        "clinical_gait":   0.15,
+        "clinical_age":    0.05,
+    },
+    "other": {
+        "mri": 0.50,
+        "eeg": 0.50,
+    },
+}
+
+
+def available_diseases() -> list[str]:
+    return sorted(DEFAULT_WEIGHTS.keys())
+
+
+def available_clinical_tests() -> list[str]:
+    """Return the bare clinical-test names (without the 'clinical_' prefix)."""
+    names: set[str] = set()
+    for table in DEFAULT_WEIGHTS.values():
+        for key in table:
+            if key.startswith("clinical_"):
+                names.add(key[len("clinical_"):])
+    return sorted(names)
+
+
+def get_weights(disease: str) -> Mapping[str, float]:
+    if disease not in DEFAULT_WEIGHTS:
+        raise KeyError(f"unknown disease: {disease!r}")
+    return DEFAULT_WEIGHTS[disease]

tests/fusion/test_weights.py

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+"""Tests for src.fusion.weights — disease/modality weight registry."""
+from __future__ import annotations
+
+import pytest
+
+from src.fusion import weights
+
+
+class TestWeights:
+    def test_available_diseases_includes_known(self) -> None:
+        diseases = set(weights.available_diseases())
+        assert {"alzheimers", "parkinsons", "other"} <= diseases
+
+    def test_available_clinical_tests_includes_each_named_input(self) -> None:
+        tests = set(weights.available_clinical_tests())
+        assert {"mmse", "moca", "updrs", "gait", "age"} <= tests
+
+    def test_get_weights_returns_nonempty_mapping(self) -> None:
+        ws = weights.get_weights("alzheimers")
+        assert ws["mri"] > 0
+        assert sum(ws.values()) == pytest.approx(1.0, abs=1e-6)
+
+    def test_get_weights_unknown_disease_raises(self) -> None:
+        with pytest.raises(KeyError, match="unknown disease"):
+            weights.get_weights("invented_disease")
+
+    def test_each_disease_weight_table_sums_to_one(self) -> None:
+        for d in weights.available_diseases():
+            assert sum(weights.get_weights(d).values()) == pytest.approx(1.0, abs=1e-6), d