fix: skip duplicate leaf creation during v3 migration

The same Wiki Page can be referenced by sidebars in multiple Wiki Spaces.
Wiki Document leaves require globally unique routes, so the second space's
migration was raising ValidationError when it tried to create another leaf
with the same wiki_page route. Skip and log instead during bench migrate.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: NagariaHussain

wiki/wiki/doctype/wiki_space/wiki_space.py

@@ -123,6 +123,22 @@ def _create_group_with_pages(self, group_label, items, sort_order):
 	def _create_page_document(self, wiki_page_name, parent_group, sort_order):
 		"""Create a leaf Wiki Document from a Wiki Page"""
 		wiki_page = frappe.get_cached_doc("Wiki Page", wiki_page_name)
+
+		# The same Wiki Page can be referenced by sidebars in multiple Wiki Spaces.
+		# Routes for leaves must be unique, so during migration the first space wins
+		# and subsequent duplicates are skipped with a log.
+		if (
+			getattr(frappe.flags, "in_migrate", False)
+			and wiki_page.route
+			and frappe.db.exists("Wiki Document", {"route": wiki_page.route, "is_group": 0})
+		):
+			print(
+				f"[wiki v3 migration] skipping duplicate leaf for Wiki Page "
+				f"'{wiki_page_name}' (route '{wiki_page.route}') in space '{self.name}': "
+				f"another sidebar already migrated this page."
+			)
+			return
+
 		leaf_doc = frappe.get_doc(
 			{
 				"doctype": "Wiki Document",