feat(overlay): awareness language wins on top of GET-15 layout [GET-16]

lib/format.ts

@@ -14,11 +14,22 @@ export function formatTokens(n: number): string {
 
 /**
  * Format cost in dollars.
- * null -> "$0.00*" (unknown model), 0.0073 -> "$0.0073", 1.5 -> "$1.50"
+ * null -> "$0.00*" (unknown model), 1.5 -> "$1.50", 100 -> "$100.00".
+ *
+ * Auto-promotes to 4 decimals when a positive fractional amount would otherwise
+ * round to "$0.00" at the default 2-decimal precision. Keeps displayed cost
+ * consistent across surfaces: a $0.0029 session reads as $0.0029 in both the
+ * overlay and the side panel, never $0.00 on one and $0.0029 on the other.
+ * Only activates when the caller accepts the default precision; explicit
+ * decimals arguments (e.g. decimals: 6) are respected as-is.
+ *
  * @param decimals - number of decimal places (default 2 for dashboard, use 4 for per-request overlay)
  */
 export function formatCost(cost: number | null, decimals: number = 2): string {
     if (cost === null) return '$0.00*';
+    if (decimals === 2 && cost > 0 && cost < 0.01) {
+        return `$${cost.toFixed(4)}`;
+    }
     return `$${cost.toFixed(decimals)}`;
 }
 

tests/audit/format-audit.test.ts

@@ -57,6 +57,19 @@ describe('formatCost', () => {
         expect(formatCost(0.0073, 4)).toBe('$0.0073');
     });
 
+    test('fractional cost under $0.01 auto-promotes to 4 decimals at default', () => {
+        expect(formatCost(0.0029)).toBe('$0.0029');
+        expect(formatCost(0.009)).toBe('$0.0090');
+    });
+
+    test('fractional cost at $0.01 boundary stays 2 decimals', () => {
+        expect(formatCost(0.01)).toBe('$0.01');
+    });
+
+    test('explicit decimals override wins over auto-promotion', () => {
+        expect(formatCost(0.0029, 4)).toBe('$0.0029');
+    });
+
     test('large cost', () => {
         expect(formatCost(100.5)).toBe('$100.50');
     });

ui/overlay-styles.ts

@@ -253,7 +253,7 @@ export const OVERLAY_CSS = `
 .lco-health-label--critical  { color: #ef4444; }
 
 .lco-coaching {
-  font-size: 9px;
+  font-size: 10px;
   line-height: 1.4;
   color: var(--lco-muted);
   margin: 2px 0 3px;

ui/overlay.ts

@@ -391,8 +391,9 @@ export function createOverlay(): OverlayHandle {
         if (elSession && sessionVisible) {
             const { requestCount, totalInputTokens, totalOutputTokens, totalCost } = state.session;
             const total = totalInputTokens + totalOutputTokens;
+            const turnLabel = requestCount === 1 ? 'turn' : 'turns';
             elSession.textContent =
-                `${requestCount} req · ~${fmt(total)} tok · ${fmtCost(totalCost)}`;
+                `${requestCount} ${turnLabel} · ~${fmt(total)} tok · ${fmtCost(totalCost)}`;
         }
 
         if (elHealth) {