initialize Electron desktop app and remove unused files

tests/client/chat-timestamp.test.ts

@@ -0,0 +1,30 @@
+import { describe, expect, it } from 'vitest'
+import { formatChatTimestamp, isSameLocalDay } from '@/utils/chat-timestamp'
+
+describe('chat timestamp formatting', () => {
+  it('shows only hour and minute for messages from today', () => {
+    const now = new Date('2026-06-18T15:30:00')
+    const messageTime = new Date('2026-06-18T09:05:00')
+
+    expect(isSameLocalDay(messageTime, now)).toBe(true)
+    expect(formatChatTimestamp(messageTime, { now, locale: 'en-US' })).toBe('09:05 AM')
+  })
+
+  it('adds month and day for previous-day messages in the same year', () => {
+    const now = new Date('2026-06-18T15:30:00')
+    const messageTime = new Date('2026-06-17T22:15:00')
+
+    expect(formatChatTimestamp(messageTime, { now, locale: 'en-US' })).toBe('06/17, 10:15 PM')
+  })
+
+  it('adds year for messages from a different year', () => {
+    const now = new Date('2026-06-18T15:30:00')
+    const messageTime = new Date('2025-12-31T23:59:00')
+
+    expect(formatChatTimestamp(messageTime, { now, locale: 'en-US' })).toBe('12/31/2025, 11:59 PM')
+  })
+
+  it('returns an empty string for invalid timestamps', () => {
+    expect(formatChatTimestamp('not a date')).toBe('')
+  })
+})