fix(tui): switch formatTimeWithSeconds to local time + add negative input guard

apps/mcp-server/src/tui/components/HeaderBar.spec.tsx

@@ -3,7 +3,7 @@ import { describe, it, expect } from 'vitest';
 import { render } from 'ink-testing-library';
 import { HeaderBar } from './HeaderBar';
 
-const FIXED_NOW = new Date('2026-03-18T14:30:45Z').getTime();
+const FIXED_NOW = new Date(2026, 2, 18, 14, 30, 45).getTime(); // local 14:30:45
 
 describe('tui/components/HeaderBar', () => {
   it('should render title with neon branding', () => {

apps/mcp-server/src/tui/components/live.pure.spec.ts

@@ -40,6 +40,11 @@ describe('tui/components/live.pure', () => {
       const now = start + 725_000; // 12분 5초
       expect(formatElapsed(start, now)).toBe('12m 5s');
     });
+
+    it('startedAt > now (clock drift) → "0s"로 클램프', () => {
+      const now = 1000000;
+      expect(formatElapsed(now + 5000, now)).toBe('0s');
+    });
   });
 
   describe('formatRelativeTime', () => {
@@ -68,6 +73,11 @@ describe('tui/components/live.pure', () => {
       expect(formatRelativeTime(now - 3600000, now)).toBe('1h ago');
       expect(formatRelativeTime(now - 7200000, now)).toBe('2h ago');
     });
+
+    it('timestamp > now (clock drift) → "just now"로 클램프', () => {
+      const now = 1000000;
+      expect(formatRelativeTime(now + 5000, now)).toBe('just now');
+    });
   });
 
   describe('spinnerFrame', () => {
@@ -177,21 +187,19 @@ describe('tui/components/live.pure', () => {
   });
 
   describe('formatTimeWithSeconds', () => {
-    it('자정 → "00:00:00"', () => {
-      // 2026-01-01T00:00:00Z = 1767225600000
-      const midnight = new Date('2026-01-01T00:00:00Z').getTime();
-      // UTC 기준
-      expect(formatTimeWithSeconds(midnight)).toBe('00:00:00');
+    it('로컬 시간 기준으로 HH:MM:SS 형식 반환', () => {
+      const d = new Date(2026, 0, 1, 14, 23, 45); // local 14:23:45
+      expect(formatTimeWithSeconds(d.getTime())).toBe('14:23:45');
     });
 
-    it('오후 시간 → "14:23:45"', () => {
-      const t = new Date('2026-01-01T14:23:45Z').getTime();
-      expect(formatTimeWithSeconds(t)).toBe('14:23:45');
+    it('한 자리 시/분/초 → 0으로 패딩', () => {
+      const d = new Date(2026, 0, 1, 3, 5, 9); // local 03:05:09
+      expect(formatTimeWithSeconds(d.getTime())).toBe('03:05:09');
     });
 
-    it('한 자리 시/분/초 → 0으로 패딩', () => {
-      const t = new Date('2026-01-01T03:05:09Z').getTime();
-      expect(formatTimeWithSeconds(t)).toBe('03:05:09');
+    it('자정 → "00:00:00"', () => {
+      const d = new Date(2026, 0, 1, 0, 0, 0); // local midnight
+      expect(formatTimeWithSeconds(d.getTime())).toBe('00:00:00');
     });
   });
 });

apps/mcp-server/src/tui/components/live.pure.ts

@@ -5,15 +5,15 @@ export interface ActivitySample {
 
 /** Format elapsed time as "Xm Ys" or "Ys". */
 export function formatElapsed(startedAt: number, now: number): string {
-  const totalSec = Math.floor((now - startedAt) / 1000);
+  const totalSec = Math.max(0, Math.floor((now - startedAt) / 1000));
   const min = Math.floor(totalSec / 60);
   const sec = totalSec % 60;
   return min > 0 ? `${min}m ${sec}s` : `${sec}s`;
 }
 
 /** Format relative time as "just now", "Ns ago", "Nm ago", "Nh ago". */
 export function formatRelativeTime(timestamp: number, now: number): string {
-  const diffSec = Math.floor((now - timestamp) / 1000);
+  const diffSec = Math.max(0, Math.floor((now - timestamp) / 1000));
   if (diffSec <= 2) return 'just now';
   if (diffSec < 60) return `${diffSec}s ago`;
   const diffMin = Math.floor(diffSec / 60);
@@ -63,11 +63,11 @@ export function computeThroughput(samples: ActivitySample[]): string {
   return `${(totalCalls / durationMin).toFixed(1)}/min`;
 }
 
-/** Format a UTC timestamp as "HH:MM:SS". */
+/** Format a timestamp as local "HH:MM:SS". */
 export function formatTimeWithSeconds(now: number): string {
   const d = new Date(now);
-  const h = String(d.getUTCHours()).padStart(2, '0');
-  const m = String(d.getUTCMinutes()).padStart(2, '0');
-  const s = String(d.getUTCSeconds()).padStart(2, '0');
+  const h = String(d.getHours()).padStart(2, '0');
+  const m = String(d.getMinutes()).padStart(2, '0');
+  const s = String(d.getSeconds()).padStart(2, '0');
   return `${h}:${m}:${s}`;
 }