refactor: extract shared types + safe chrome wrappers into src/lib

- src/lib/types.ts: message contract (both ANALYZE_TEXT shapes preserved),
  config/response types, storage-key constants.
- src/lib/messaging.ts: single safeStorageGet/safeStorageSet/safeSendMessage/
  isExtensionValid implementation replacing the three divergent copies in
  Options, Popup, and content. Content script keeps its refresh-toast
  behavior via an onContextInvalidated callback.
- New '@lib' import alias (wxt force-overwrites '~' and '@' to srcDir, so
  those cannot point at ./src); wired in wxt.config, tsconfig, vitest.
- tests/unit/messaging.test.ts: 14 unit tests over the wrappers.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

entrypoints/background.ts

@@ -1,5 +1,6 @@
 import { defineBackground } from 'wxt/utils/define-background';
 import nacl from 'tweetnacl';
+import type { AnalyzePayload, LexAIConfig, LexAIResponse } from '@lib/types';
 
 // ─── Fetch with timeout ───────────────────────────────────────────────────────
 
@@ -13,27 +14,6 @@ async function fetchWithTimeout(url: string, options: RequestInit, timeoutMs = 3
   }
 }
 
-// ─── Types ────────────────────────────────────────────────────────────────────
-
-interface AnalyzePayload {
-  text: string;
-  action: string;
-  style?: string;
-}
-
-interface LexAIConfig {
-  provider?: string;
-  apiKey?: string;
-  apiKeyEnc?: string;
-  encKey?: string;
-  model?: string;
-}
-
-interface LexAIResponse {
-  result?: string;
-  error?: string;
-}
-
 // ─── System prompts ───────────────────────────────────────────────────────────
 
 function getSystemPrompt(action: string, style?: string): string {

entrypoints/content.ts

@@ -1,4 +1,5 @@
 import { defineContentScript } from 'wxt/utils/define-content-script';
+import { isExtensionValid, safeSendMessage } from '@lib/messaging';
 
 export default defineContentScript({
   matches: ['<all_urls>'],
@@ -362,15 +363,7 @@ export default defineContentScript({
       }
     }
 
-    // ─── Extension context guard ──────────────────────────────────────────────
-
-    function isExtensionValid(): boolean {
-      try {
-        return typeof chrome !== 'undefined' && !!chrome.runtime?.id;
-      } catch {
-        return false;
-      }
-    }
+    // Extension context guard: isExtensionValid is imported from ~/lib/messaging.
 
     function showErrorToast(msg: string) {
       const toast = document.createElement('div');
@@ -528,7 +521,7 @@ export default defineContentScript({
           grid.style.display       = 'none';
           spinnerSlot.style.display = 'flex';
 
-          const response = await safeSendMessage({
+          const response = await sendToBackground({
             type:   'COPY_AS',
             text,
             format: fmt,
@@ -563,22 +556,13 @@ export default defineContentScript({
     }
 
     // ─── Safe chrome.runtime.sendMessage wrapper ──────────────────────────────
+    // Shared implementation; on a stale extension context we toast and clean up.
 
-    async function safeSendMessage(payload: Record<string, unknown>): Promise<unknown> {
-      if (!isExtensionValid()) {
+    async function sendToBackground(payload: Record<string, unknown>): Promise<unknown> {
+      return safeSendMessage(payload, () => {
         showErrorToast('LexAI was updated — please refresh this page.');
-        return null;
-      }
-      try {
-        return await chrome.runtime.sendMessage(payload);
-      } catch (err) {
-        if (String(err).includes('Extension context invalidated') ||
-            String(err).includes('message channel closed')) {
-          showErrorToast('LexAI was updated — please refresh this page.');
-          hideToolbar();
-        }
-        return null;
-      }
+        hideToolbar();
+      });
     }
 
     // ─── LLM call ─────────────────────────────────────────────────────────────
@@ -628,14 +612,14 @@ export default defineContentScript({
       }
 
       try {
-        const response = await safeSendMessage({
+        const response = await sendToBackground({
           type:    'ANALYZE_TEXT',
           payload: { text: textToProcess, action, style: currentStyle },
         }) as { error?: string; result?: string } | null;
 
         hideToolbar();
 
-        if (response === null) return; // safeSendMessage already handled the error
+        if (response === null) return; // sendToBackground already handled the error
 
         if (response?.error) {
           showModal(`❌ ${response.error}`, null, snapStart, snapEnd, snapElement, snapRange, action, textToProcess);
@@ -832,7 +816,7 @@ export default defineContentScript({
         regenBtn.disabled = true;
         styleSelect.disabled = true;
 
-        const response = await safeSendMessage({
+        const response = await sendToBackground({
           type:    'ANALYZE_TEXT',
           payload: { text: textForRegenerate, action, style: chosenStyle },
         }) as { error?: string; result?: string } | null;

entrypoints/options/Options.tsx

@@ -1,6 +1,7 @@
 import React, { useEffect, useRef, useState } from 'react';
 import { createRoot } from 'react-dom/client';
 import nacl from 'tweetnacl';
+import { safeSendMessage, safeStorageGet, safeStorageSet } from '@lib/messaging';
 
 // ─── Provider config ──────────────────────────────────────────────────────────
 
@@ -166,40 +167,6 @@ const styles = {
   } as React.CSSProperties,
 };
 
-// ─── Safe chrome storage wrappers ────────────────────────────────────────────
-
-function safeStorageGet(keys: string[], callback: (result: Record<string, string>) => void) {
-  try {
-    if (typeof chrome === 'undefined' || !chrome.runtime?.id) return;
-    chrome.storage.local.get(keys, callback);
-  } catch (err) {
-    console.warn('LexAI: Extension context invalidated', err);
-  }
-}
-
-function safeStorageSet(data: Record<string, string>, callback?: () => void) {
-  try {
-    if (typeof chrome === 'undefined' || !chrome.runtime?.id) return;
-    if (callback) {
-      chrome.storage.local.set(data, callback);
-    } else {
-      chrome.storage.local.set(data);
-    }
-  } catch (err) {
-    console.warn('LexAI: Extension context invalidated', err);
-  }
-}
-
-async function safeSendMessage(message: Record<string, unknown>): Promise<any> {
-  try {
-    if (typeof chrome === 'undefined' || !chrome.runtime?.id) return null;
-    return await chrome.runtime.sendMessage(message);
-  } catch (err) {
-    console.warn('LexAI: sendMessage failed', err);
-    return null;
-  }
-}
-
 // ─── Component ────────────────────────────────────────────────────────────────
 
 function OptionsPage() {

entrypoints/popup/Popup.tsx

@@ -1,41 +1,6 @@
 import React, { useEffect, useRef, useState } from 'react';
 import { createRoot } from 'react-dom/client';
-
-// ─── Safe chrome storage wrapper ─────────────────────────────────────────────
-
-function safeStorageGet(
-  storage: chrome.storage.StorageArea,
-  keys: string[],
-  callback: (result: Record<string, string>) => void,
-) {
-  try {
-    if (typeof chrome === 'undefined' || !chrome.runtime?.id) return;
-    storage.get(keys, callback);
-  } catch (err) {
-    console.warn('LexAI: Extension context invalidated', err);
-  }
-}
-
-function safeStorageSet(storage: chrome.storage.StorageArea, data: Record<string, string>) {
-  try {
-    if (typeof chrome === 'undefined' || !chrome.runtime?.id) return;
-    storage.set(data);
-  } catch (err) {
-    console.warn('LexAI: Extension context invalidated', err);
-  }
-}
-
-async function safeSendMessage(
-  message: Record<string, unknown>,
-): Promise<Record<string, string> | null> {
-  try {
-    if (typeof chrome === 'undefined' || !chrome.runtime?.id) return null;
-    return await chrome.runtime.sendMessage(message);
-  } catch (err) {
-    console.warn('LexAI: sendMessage failed', err);
-    return null;
-  }
-}
+import { safeSendMessage, safeStorageGet, safeStorageSet } from '@lib/messaging';
 
 // ─── Constants ───────────────────────────────────────────────────────────────
 
@@ -222,7 +187,7 @@ function Popup() {
 
   // Load config + restore session input + load writing style
   useEffect(() => {
-    safeStorageGet(chrome.storage.local, ['provider', 'apiKey', 'apiKeyEnc', 'model', 'writingStyle'], (result) => {
+    safeStorageGet(['provider', 'apiKey', 'apiKeyEnc', 'model', 'writingStyle'], (result) => {
       if (result.apiKey || result.apiKeyEnc) {
         setConfigured(true);
         setProvider(result.provider || 'openai');
@@ -235,11 +200,11 @@ function Popup() {
 
     if (!sessionRestored.current) {
       sessionRestored.current = true;
-      safeStorageGet(chrome.storage.session, ['lexai_popup_input'], (res) => {
+      safeStorageGet(['lexai_popup_input'], (res) => {
         if (res.lexai_popup_input) {
           setInputText(res.lexai_popup_input);
         }
-      });
+      }, chrome.storage.session);
     }
   }, []);
 
@@ -247,14 +212,14 @@ function Popup() {
   const handleInputChange = (e: React.ChangeEvent<HTMLTextAreaElement>) => {
     const val = e.target.value;
     setInputText(val);
-    safeStorageSet(chrome.storage.session, { lexai_popup_input: val });
+    safeStorageSet({ lexai_popup_input: val }, undefined, chrome.storage.session);
   };
 
   // Save writing style on change
   const handleStyleChange = (e: React.ChangeEvent<HTMLSelectElement>) => {
     const val = e.target.value;
     setWritingStyle(val);
-    safeStorageSet(chrome.storage.local, { writingStyle: val });
+    safeStorageSet({ writingStyle: val });
   };
 
   const openSettings = () => {