feat: unified shell, diagnostics pack, native Office, sticky board

Make Surface remote debugging and classroom workflows viable: always-on
structured logs with one-click zip export, a single AppShell chrome,
OOXML PPTX/DOCX annotation without LibreOffice, and a first-class sticky
board. Also drop spike/legacy ink widgets and tighten pen feel
(predictor, PenInfoHistory, page-tile layer).

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

lib/l10n/app_zh.arb

@@ -97,6 +97,18 @@
   "failedToOpenPdf": "打开 PDF 失败：\n{error}",
   "pdfNoPages": "PDF 没有任何页面。",
   "pageOfPages": "{current} / {total}",
+  "libraryTab": "库",
+  "boardTab": "便利贴",
+  "shellTagline": "手写 · 批注 · 知识",
+  "notesSection": "笔记",
+  "documentsSection": "文档",
+  "emptyLibraryTitle": "还没有内容",
+  "emptyLibraryBody": "新建笔记，或导入 PDF / PPT / Word",
+  "diagnosticsSection": "诊断",
+  "diagnosticsExport": "导出诊断包",
+  "diagnosticsExportHint": "在 Surface 上复现问题后导出，发回给开发者分析",
+  "diagnosticsToggle": "输入诊断叠加层",
+  "penSettingsUnified": "笔与墨迹",
   "board": "便利贴板",
   "boardTitle": "便利贴板",
   "boardOpen": "便利贴板",