Develop (#55)

feat: optimize dashboard/search UX and simplify extension architecture

Redesign Dashboard with compact tool grid and recently used tools
Improve TopBar search UX with Cmd/Ctrl+K shortcut and better history navigation
Reorganize project structure into src/
Migrate i18n from react-i18next to chrome.i18n
Remove runtime language switch and settings page
Remove HTML/Markdown conversion tools
Clean up unused code, dead animations, redundant comments, and imports
Improve component consistency with shadcn/ui patterns
Replace hardcoded strings/colors with i18n tokens and theme tokens
Add comprehensive project documentation and coding standards
Fix CI artifact upload workflow and multiple TypeScript/test issues

Includes various refactors, UI polish, i18n cleanup, CI improvements,
and maintenance updates across the codebase.

src/entrypoints/content/contextMenuHandler.ts

@@ -0,0 +1,80 @@
+import type { ContextMenuClickedPayload } from '@/utils/messages';
+import { MessageAction, onMessage } from '@/utils/messages';
+import { getTextStats } from '@/utils/textStatistics';
+import { hidePopover, showTextStatsResult, showTimestampResult } from './uiPopover';
+
+function getI18nText(key: string, fallback: string): string {
+  if (typeof chrome !== 'undefined' && chrome.i18n) {
+    return chrome.i18n.getMessage(key) || fallback;
+  }
+  return fallback;
+}
+
+function convertTimestamp(input: string): string {
+  const invalidText = getI18nText('invalidTimestamp', 'Invalid Timestamp');
+  const num = Number(input.trim());
+
+  if (isNaN(num)) {
+    return invalidText;
+  }
+
+  // 1e12 判定毫秒级/秒级时间戳兼容
+  const d = num > 1e12 ? new Date(num) : new Date(num * 1000);
+
+  if (isNaN(d.getTime())) {
+    return invalidText;
+  }
+
+  const year = d.getFullYear();
+  const month = String(d.getMonth() + 1).padStart(2, '0');
+  const day = String(d.getDate()).padStart(2, '0');
+  const hours = String(d.getHours()).padStart(2, '0');
+  const minutes = String(d.getMinutes()).padStart(2, '0');
+  const seconds = String(d.getSeconds()).padStart(2, '0');
+
+  return `${year}/${month}/${day} ${hours}:${minutes}:${seconds}`;
+}
+
+let lastClickX = 0;
+let lastClickY = 0;
+
+document.addEventListener(
+  'contextmenu',
+  (e) => {
+    lastClickX = e.clientX;
+    lastClickY = e.clientY;
+  },
+  { capture: true, passive: true },
+);
+
+export function initContextMenuHandler(): void {
+  const dismissPopover = (): void => {
+    hidePopover();
+  };
+
+  document.addEventListener('click', dismissPopover, { passive: true });
+  document.addEventListener('scroll', dismissPopover, { passive: true });
+  window.addEventListener('resize', dismissPopover, { passive: true });
+
+  onMessage(MessageAction.CONTEXT_MENU_CLICKED, (message) => {
+    const { featureKey, payload } = message.data as ContextMenuClickedPayload;
+
+    switch (featureKey) {
+      case 'timestamp': {
+        const result = convertTimestamp(payload);
+        showTimestampResult(lastClickX, lastClickY, payload, result);
+        break;
+      }
+
+      case 'textStatistics': {
+        const stats = getTextStats(payload);
+        showTextStatsResult(lastClickX, lastClickY, payload, stats);
+        break;
+      }
+
+      default:
+        hidePopover();
+        break;
+    }
+  });
+}