fix: type error on tiptap-markdown storage access

Cast editor storage to Record<string, any> since tiptap-markdown
does not ship type declarations for its storage extension.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/lib/components/TiptapEditor.svelte

@@ -34,7 +34,8 @@
 			],
 			content,
 			onUpdate: ({ editor: e }) => {
-				onUpdate(e.storage.markdown.getMarkdown());
+				// eslint-disable-next-line @typescript-eslint/no-explicit-any
+				onUpdate((e.storage as Record<string, any>).markdown.getMarkdown());
 			},
 			onTransaction: () => {
 				// Trigger Svelte reactivity for active state checks