feat: Added getTierLabel() helper, gradient track fill via --slider-fil…

- "frontend/src/components/ChatWidget.tsx"
- "frontend/src/components/ChatWidget.module.css"

GSD-Task: S04/T02

.gsd/milestones/M023/slices/S04/S04-PLAN.md

@@ -25,7 +25,7 @@ Update existing test `test_personality_prompt_injected_when_weight_and_profile`
   - Estimate: 45m
   - Files: backend/chat_service.py, backend/tests/test_chat.py
   - Verify: cd backend && python -m pytest tests/test_chat.py -v -k personality
-- [ ] **T02: Enhance slider UX with dynamic tier label, value indicator, and gradient track** — Enhance the personality slider in ChatWidget.tsx with three visual feedback features:
+- [x] **T02: Added getTierLabel() helper, gradient track fill via --slider-fill CSS custom property, and centered tier label + numeric value below the personality slider** — Enhance the personality slider in ChatWidget.tsx with three visual feedback features:
 
 1. **Dynamic tier label**: Below the slider, show a centered label that changes based on current weight value:
    - 0.0–0.19: "Encyclopedic"

.gsd/milestones/M023/slices/S04/tasks/T01-VERIFY.json

@@ -0,0 +1,24 @@
+{
+  "schemaVersion": 1,
+  "taskId": "T01",
+  "unitId": "M023/S04/T01",
+  "timestamp": 1775297087024,
+  "passed": false,
+  "discoverySource": "task-plan",
+  "checks": [
+    {
+      "command": "cd backend",
+      "exitCode": 0,
+      "durationMs": 11,
+      "verdict": "pass"
+    },
+    {
+      "command": "python -m pytest tests/test_chat.py -v -k personality",
+      "exitCode": 4,
+      "durationMs": 264,
+      "verdict": "fail"
+    }
+  ],
+  "retryAttempt": 1,
+  "maxRetries": 2
+}

.gsd/milestones/M023/slices/S04/tasks/T02-SUMMARY.md

@@ -0,0 +1,79 @@
+---
+id: T02
+parent: S04
+milestone: M023
+provides: []
+requires: []
+affects: []
+key_files: ["frontend/src/components/ChatWidget.tsx", "frontend/src/components/ChatWidget.module.css"]
+key_decisions: ["Wrapped sliderRow in sliderSection container for clean grouping", "Used CSS custom property --slider-fill via inline style for gradient track", "Tabular-nums on tier value for stable width"]
+patterns_established: []
+drill_down_paths: []
+observability_surfaces: []
+duration: ""
+verification_result: "Frontend build passes clean (cd frontend && npm run build, exit 0). Backend personality tests all pass (cd backend && python -m pytest tests/test_chat.py -v -k personality, 11/11 passed)."
+completed_at: 2026-04-04T10:06:38.357Z
+blocker_discovered: false
+---
+
+# T02: Added getTierLabel() helper, gradient track fill via --slider-fill CSS custom property, and centered tier label + numeric value below the personality slider
+
+> Added getTierLabel() helper, gradient track fill via --slider-fill CSS custom property, and centered tier label + numeric value below the personality slider
+
+## What Happened
+---
+id: T02
+parent: S04
+milestone: M023
+key_files:
+  - frontend/src/components/ChatWidget.tsx
+  - frontend/src/components/ChatWidget.module.css
+key_decisions:
+  - Wrapped sliderRow in sliderSection container for clean grouping
+  - Used CSS custom property --slider-fill via inline style for gradient track
+  - Tabular-nums on tier value for stable width
+duration: ""
+verification_result: passed
+completed_at: 2026-04-04T10:06:38.357Z
+blocker_discovered: false
+---
+
+# T02: Added getTierLabel() helper, gradient track fill via --slider-fill CSS custom property, and centered tier label + numeric value below the personality slider
+
+**Added getTierLabel() helper, gradient track fill via --slider-fill CSS custom property, and centered tier label + numeric value below the personality slider**
+
+## What Happened
+
+Three visual feedback enhancements to the personality slider: getTierLabel() maps weight ranges to 5 tier labels matching the backend interpolation tiers; gradient track fill via --slider-fill CSS custom property on both webkit and moz pseudo-elements; centered tier info row with label and tabular-nums numeric value. Wrapped sliderRow in sliderSection container for clean grouping.
+
+## Verification
+
+Frontend build passes clean (cd frontend && npm run build, exit 0). Backend personality tests all pass (cd backend && python -m pytest tests/test_chat.py -v -k personality, 11/11 passed).
+
+## Verification Evidence
+
+| # | Command | Exit Code | Verdict | Duration |
+|---|---------|-----------|---------|----------|
+| 1 | `cd frontend && npm run build` | 0 | ✅ pass | 6800ms |
+| 2 | `cd backend && python -m pytest tests/test_chat.py -v -k personality` | 0 | ✅ pass | 3900ms |
+
+
+## Deviations
+
+Added .sliderSection wrapper div to group slider row and tier info under one border-bottom — minor structural improvement not in original plan.
+
+## Known Issues
+
+None.
+
+## Files Created/Modified
+
+- `frontend/src/components/ChatWidget.tsx`
+- `frontend/src/components/ChatWidget.module.css`
+
+
+## Deviations
+Added .sliderSection wrapper div to group slider row and tier info under one border-bottom — minor structural improvement not in original plan.
+
+## Known Issues
+None.

frontend/src/components/ChatWidget.module.css

@@ -69,13 +69,16 @@
 
 /* ── Personality slider ───────────────────────────────────── */
 
+.sliderSection {
+  padding: 0.5rem 1rem;
+  border-bottom: 1px solid var(--color-border);
+  flex-shrink: 0;
+}
+
 .sliderRow {
   display: flex;
   align-items: center;
   gap: 0.5rem;
-  padding: 0.5rem 1rem;
-  border-bottom: 1px solid var(--color-border);
-  flex-shrink: 0;
 }
 
 .sliderLabel {
@@ -91,7 +94,11 @@
   appearance: none;
   height: 4px;
   border-radius: 2px;
-  background: var(--color-border);
+  background: linear-gradient(
+    to right,
+    var(--color-accent) var(--slider-fill, 0%),
+    var(--color-border) var(--slider-fill, 0%)
+  );
   outline: none;
   cursor: pointer;
 }
@@ -126,7 +133,35 @@
 .slider::-moz-range-track {
   height: 4px;
   border-radius: 2px;
-  background: var(--color-border);
+  background: linear-gradient(
+    to right,
+    var(--color-accent) var(--slider-fill, 0%),
+    var(--color-border) var(--slider-fill, 0%)
+  );
+}
+
+/* ── Tier label + value ───────────────────────────────────── */
+
+.tierInfo {
+  display: flex;
+  justify-content: center;
+  align-items: baseline;
+  gap: 0.375rem;
+  padding-top: 0.25rem;
+}
+
+.tierLabel {
+  font-size: 0.6875rem;
+  font-weight: 600;
+  color: var(--color-text-secondary);
+  transition: color 0.2s;
+}
+
+.tierValue {
+  font-size: 0.625rem;
+  color: var(--color-text-secondary);
+  opacity: 0.6;
+  font-variant-numeric: tabular-nums;
 }
 
 .headerTitle {

frontend/src/components/ChatWidget.tsx

@@ -115,6 +115,15 @@ function parseCitations(text: string, sources: ChatSource[]): React.ReactNode[]
   return nodes.length > 0 ? nodes : [text];
 }
 
+/** Map personality weight to a human-readable tier label. */
+function getTierLabel(weight: number): string {
+  if (weight < 0.2) return "Encyclopedic";
+  if (weight < 0.4) return "Subtle Reference";
+  if (weight < 0.6) return "Creator Tone";
+  if (weight < 0.8) return "Creator Voice";
+  return "Full Embodiment";
+}
+
 export default function ChatWidget({ creatorName, techniques }: ChatWidgetProps) {
   const [open, setOpen] = useState(false);
   const [messages, setMessages] = useState<Message[]>([]);
@@ -275,19 +284,26 @@ export default function ChatWidget({ creatorName, techniques }: ChatWidgetProps)
         </div>
 
         {/* Personality slider */}
-        <div className={styles.sliderRow}>
+        <div className={styles.sliderSection}>
-          <span className={styles.sliderLabel}>Encyclopedic</span>
+          <div className={styles.sliderRow}>
-          <input
+            <span className={styles.sliderLabel}>Encyclopedic</span>
-            type="range"
+            <input
-            className={styles.slider}
+              type="range"
-            min={0}
+              className={styles.slider}
-            max={1}
+              min={0}
-            step={0.1}
+              max={1}
-            value={personalityWeight}
+              step={0.1}
-            onChange={(e) => setPersonalityWeight(parseFloat(e.target.value))}
+              value={personalityWeight}
-            aria-label="Personality weight"
+              onChange={(e) => setPersonalityWeight(parseFloat(e.target.value))}
-          />
+              aria-label="Personality weight"
-          <span className={styles.sliderLabel}>Creator Voice</span>
+              style={{ '--slider-fill': `${personalityWeight * 100}%` } as React.CSSProperties}
+            />
+            <span className={styles.sliderLabel}>Creator Voice</span>
+          </div>
+          <div className={styles.tierInfo}>
+            <span className={styles.tierLabel}>{getTierLabel(personalityWeight)}</span>
+            <span className={styles.tierValue}>{personalityWeight.toFixed(1)}</span>
+          </div>
         </div>
 
         {/* Messages */}