fix(drafts): wait for the fork POST to land before navigating

OtherUsersDraftsModal's Fork action called UserDraft.save, which routes
through the autosave debouncer (1500ms). The subsequent goto fired
within the same tick, so the destination editor's get_draft=true read
ran before the POST landed and 404'd — refreshing worked because by
then the debounced save had fired.

Call UserDraftDbSyncer.save with immediate: true and await it. The
syncer cancels any queued debouncer task for the key and resolves the
promise only after the POST completes, so the route load can find the
forked draft on the first try.

frontend/src/lib/components/common/confirmationModal/OtherUsersDraftsModal.svelte

@@ -18,7 +18,7 @@
 	import Modal2 from '$lib/components/common/modal/Modal2.svelte'
 	import Button from '$lib/components/common/button/Button.svelte'
 	import Tooltip from '$lib/components/Tooltip.svelte'
-	import { UserDraft } from '$lib/userDraft.svelte'
+	import { UserDraftDbSyncer } from '$lib/userDraftDbSyncer.svelte'
 
 	export type OtherDraftUser = { username?: string | null }
 
@@ -94,7 +94,19 @@
 		try {
 			const value = await fetchDraft(owner)
 			const target = forkPath(owner)
-			UserDraft.save(itemKind, target, value, { workspace })
+			// Bypass the autosave debouncer so the fork lands on the
+			// server BEFORE we navigate. The destination route loads
+			// via `getDraft=true` and 404s if no draft yet exists at
+			// the fork path — the prior `UserDraft.save` call
+			// scheduled a debounced POST 1.5s out, so a fresh nav was
+			// always too early.
+			await UserDraftDbSyncer.save({
+				workspace,
+				itemKind,
+				path: target,
+				value,
+				immediate: true
+			})
 			isOpen = false
 			goto(editPathFor(target))
 		} catch (e) {