refactor: web-to-pixso → web-to-ppt 全面改名

- 目录 web-to-pixso/ → web-to-ppt/
- 所有代码引用：PIXSO → WEB_TO_PPT, webToPixso → webToPPT
- 数据格式：pixso-design-capture → web-to-ppt-capture
- CSS 选择器：__web_to_pixso_ → __web_to_ppt_
- README 重写，移除 Pixso 相关描述
- docs/web-to-pixso-mapping.md → docs/web-to-ppt-mapping.md

web-to-ppt/manifest.json

@@ -0,0 +1,33 @@
+{
+  "manifest_version": 3,
+  "name": "Web to PPT",
+  "version": "2.0.0",
+  "description": "Capture a webpage and export it as an editable PPTX presentation.",
+  "permissions": ["activeTab", "scripting", "downloads", "storage"],
+  "host_permissions": ["<all_urls>"],
+  "background": {
+    "service_worker": "background.js"
+  },
+  "action": {
+    "default_title": "Web to PPT",
+    "default_popup": "popup.html",
+    "default_icon": {
+      "16": "logo/plugin-logo.png",
+      "32": "logo/plugin-logo.png",
+      "48": "logo/plugin-logo.png",
+      "128": "logo/plugin-logo.png"
+    }
+  },
+  "icons": {
+    "16": "logo/plugin-logo.png",
+    "32": "logo/plugin-logo.png",
+    "48": "logo/plugin-logo.png",
+    "128": "logo/plugin-logo.png"
+  },
+  "web_accessible_resources": [
+    {
+      "resources": ["capture.js", "runner.js", "lib-pptxgen.js", "convert-browser.js"],
+      "matches": ["<all_urls>"]
+    }
+  ]
+}