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>

windows/runner/pen_channel.cpp

@@ -89,6 +89,7 @@ void ObservePenMessage(UINT message, WPARAM wparam, LPARAM lparam) {
   int raw_pen_flags = 0;
   int raw_pen_mask = 0;
   int btn_change = 0;
+  int history_count = 0;
 
   if (is_pointer) {
     ++g_ptr_msgs;
@@ -124,6 +125,13 @@ void ObservePenMessage(UINT message, WPARAM wparam, LPARAM lparam) {
         const int ay = ppi.tiltY < 0 ? -ppi.tiltY : ppi.tiltY;
         if (ax > g_tilt_abs_max) g_tilt_abs_max = ax;
         if (ay > g_tilt_abs_max) g_tilt_abs_max = ay;
+
+        // Coalesce recent history (diagnostic + future batching).
+        POINTER_PEN_INFO history[32];
+        UINT32 hist_n = 32;
+        if (GetPointerPenInfoHistory(pointerId, &hist_n, history)) {
+          history_count = static_cast<int>(hist_n);
+        }
       }
     }
     if (message == WM_POINTERUP) {
@@ -151,6 +159,7 @@ void ObservePenMessage(UINT message, WPARAM wparam, LPARAM lparam) {
       {flutter::EncodableValue("orPenMask"), flutter::EncodableValue(g_pen_mask_or)},
       {flutter::EncodableValue("btnChangeLast"), flutter::EncodableValue(g_btn_change_last)},
       {flutter::EncodableValue("tiltAbsMax"), flutter::EncodableValue(g_tilt_abs_max)},
+      {flutter::EncodableValue("historyCount"), flutter::EncodableValue(history_count)},
   };
   g_pen_sink->Success(flutter::EncodableValue(payload));
 }