feat(w3): ship v1.4.0 export matrix, cockpit tasks, and focus ambient

Add ExportMatrixService for txt/md/docx/pdf, extend ExportModal, cockpit outline tasks, focus ambient sound, and E2E-PDF-01 with 134 passing unit tests.

Co-authored-by: Cursor <cursoragent@cursor.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "bilin",
-  "version": "1.3.0",
+  "version": "1.4.0",
   "description": "笔临 - 长篇创作智能协作平台",
   "main": "./out/main/index.js",
   "type": "module",
@@ -32,6 +32,7 @@
     "cytoscape": "^3.34.0",
     "cytoscape-cose-bilkent": "^4.1.0",
     "diff-match-patch": "^1.0.5",
+    "docx": "^9.7.1",
     "electron": "^36.9.0",
     "extract-zip": "^2.0.1",
     "i18next": "^24.2.3",