fix: decouple the sentiment weight from the base mix in the weights form

Sentiment is now a signed adjustment (± points on top of the base), not part of
the averaged dimensions — but the weights form still squeezed all five sliders to
sum to 100%, so dragging sentiment rebalanced the base and you couldn't set a clean
±N. Now the four base dimensions normalize among themselves (share shown as %),
and sentiment is its own "influence (± points)" control passed through raw
(slider 10 → weight 0.10 → ±10), independent of the base.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/components/rankings/WeightsForm.tsx

@@ -1,12 +1,16 @@
-import { useState, useMemo, type FormEvent } from 'react';
+import { useState, type FormEvent } from 'react';
 import { useUpdateWeights } from '../../hooks/useScores';
 
 interface WeightsFormProps {
   weights: Record<string, number>;
 }
 
+const SENTIMENT = 'sentiment';
+
 export function WeightsForm({ weights }: WeightsFormProps) {
-  // Convert API decimal weights (0-1) to 0-100 integer scale on mount
+  // API decimal weights (0-1) → 0-100 integer sliders. For the base dimensions
+  // that's their share of the weighted average; for sentiment it's the ± points
+  // it can move the composite (MAX_ADJ), decoupled from the base mix.
   const [sliderValues, setSliderValues] = useState<Record<string, number>>(() =>
     Object.fromEntries(
       Object.entries(weights).map(([key, w]) => [key, Math.round(w * 100)])
@@ -14,10 +18,10 @@ export function WeightsForm({ weights }: WeightsFormProps) {
   );
   const updateWeights = useUpdateWeights();
 
-  const allZero = useMemo(
-    () => Object.values(sliderValues).every((v) => v === 0),
-    [sliderValues]
-  );
+  const baseKeys = Object.keys(weights).filter((k) => k !== SENTIMENT);
+  const hasSentiment = SENTIMENT in weights;
+  const baseTotal = baseKeys.reduce((sum, k) => sum + (sliderValues[k] ?? 0), 0);
+  const sentimentPts = sliderValues[SENTIMENT] ?? 0;
 
   const handleChange = (key: string, value: string) => {
     const num = parseInt(value, 10);
@@ -26,24 +30,35 @@ export function WeightsForm({ weights }: WeightsFormProps) {
 
   const handleSubmit = (e: FormEvent) => {
     e.preventDefault();
-    if (allZero) return;
+    if (baseTotal === 0) return;
 
-    const total = Object.values(sliderValues).reduce((sum, v) => sum + v, 0);
-    const normalized = Object.fromEntries(
-      Object.entries(sliderValues).map(([key, v]) => [key, v / total])
+    // Base dimensions normalize among themselves; sentiment passes through raw
+    // (slider value / 100) so it stays independent of the base.
+    const payload: Record<string, number> = Object.fromEntries(
+      baseKeys.map((key) => [key, (sliderValues[key] ?? 0) / baseTotal])
     );
-    updateWeights.mutate(normalized);
+    if (hasSentiment) payload[SENTIMENT] = sentimentPts / 100;
+    updateWeights.mutate(payload);
   };
 
   return (
     <form onSubmit={handleSubmit} className="glass p-5">
-      <h3 className="mb-4 text-xs font-semibold uppercase tracking-widest text-gray-500">
+      <h3 className="mb-1 text-xs font-semibold uppercase tracking-widest text-gray-500">
         Scoring Weights
       </h3>
+      <p className="mb-4 text-[11px] text-gray-500">
+        The base dimensions are a weighted average (shares normalize to 100%). Sentiment is applied
+        separately as a signed adjustment on top.
+      </p>
       <div className="grid grid-cols-1 gap-3 sm:grid-cols-2 lg:grid-cols-3">
-        {Object.keys(weights).map((key) => (
+        {baseKeys.map((key) => (
           <label key={key} className="flex flex-col gap-1.5">
-            <span className="text-xs text-gray-400 capitalize">{key.replace(/_/g, ' ')}</span>
+            <span className="text-xs text-gray-400 capitalize">
+              {key.replace(/_/g, ' ')}
+              <span className="ml-1 text-gray-600">
+                · {baseTotal > 0 ? Math.round(((sliderValues[key] ?? 0) / baseTotal) * 100) : 0}%
+              </span>
+            </span>
             <div className="flex items-center gap-2">
               <input
                 type="range"
@@ -61,14 +76,39 @@ export function WeightsForm({ weights }: WeightsFormProps) {
           </label>
         ))}
       </div>
-      {allZero && (
-        <p className="mt-3 text-xs text-red-400">
-          At least one weight must be greater than zero
-        </p>
+
+      {hasSentiment && (
+        <div className="mt-4 border-t border-white/[0.06] pt-4">
+          <label className="flex flex-col gap-1.5">
+            <span className="text-xs text-gray-400">Sentiment influence (± points)</span>
+            <div className="flex items-center gap-2 sm:max-w-sm">
+              <input
+                type="range"
+                min={0}
+                max={30}
+                step={1}
+                value={sentimentPts}
+                onChange={(e) => handleChange(SENTIMENT, e.target.value)}
+                className="h-2 w-full cursor-pointer appearance-none rounded-lg bg-gray-700 accent-blue-500"
+              />
+              <span className="min-w-[3ch] text-right text-sm font-medium text-gray-300">
+                ±{sentimentPts}
+              </span>
+            </div>
+            <span className="text-[11px] text-gray-600">
+              Max points a bullish (or bearish) read moves the composite, scaled by confidence.
+              Doesn&rsquo;t change the base mix. 0 = ignore sentiment.
+            </span>
+          </label>
+        </div>
+      )}
+
+      {baseTotal === 0 && (
+        <p className="mt-3 text-xs text-red-400">At least one base weight must be greater than zero</p>
       )}
       <button
         type="submit"
-        disabled={updateWeights.isPending || allZero}
+        disabled={updateWeights.isPending || baseTotal === 0}
         className="mt-4 btn-primary px-4 py-2 text-sm disabled:opacity-50"
       >
         <span>{updateWeights.isPending ? 'Updating…' : 'Update Weights'}</span>