fix: restore PDF pen capture and overhaul sticky/pens/pages

Reinstall PenCaptureBinding so stylus ink hits again; keep finger Listener translucent under pinch; page-anchor sticky with drag/resize; OneNote pen slots (brush+width+color); blank-note multi-page; default side button to hold-select-text.

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

lib/services/vault_service.dart

@@ -265,6 +265,7 @@ class VaultService {
       BadnoteSidecar(
         docType: 'notebook',
         title: pageTitle,
+        pageCount: 1,
         createdAt: now,
         updatedAt: now,
       ),
@@ -311,6 +312,7 @@ class VaultService {
       BadnoteSidecar(
         docType: 'notebook',
         title: title,
+        pageCount: 1,
         createdAt: now,
         updatedAt: now,
       ),
@@ -414,6 +416,7 @@ class VaultService {
     final sidecar = BadnoteSidecar(
       docType: 'notebook',
       title: trimmed.isEmpty ? null : trimmed,
+      pageCount: 1,
       createdAt: now,
       updatedAt: now,
     );