fix(journey-editor): clear liveAnnounce 500ms after move; document svelte-ignore suppressions

NVDA+Chrome and VoiceOver+Safari can re-announce a persistent non-empty
aria-live region when adjacent DOM mutations occur. Clearing with a
500ms delay gives the announcement time to fire once before going quiet.

The two svelte-ignore a11y_no_static_element_interactions suppressions are
given preceding comments explaining the keyboard accessibility contract so
they are not mistaken for unaddressed tech debt.

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

frontend/src/lib/geschichte/JourneyEditor.svelte

@@ -155,6 +155,10 @@ async function handleMoveUp(index: number) {
 		newPosition: index
 	});
 	await handleReorder(ids);
+	// Clear so the live region does not re-announce on unrelated DOM mutations
+	setTimeout(() => {
+		liveAnnounce = '';
+	}, 500);
 }
 
 async function handleMoveDown(index: number) {
@@ -167,6 +171,10 @@ async function handleMoveDown(index: number) {
 		newPosition: index + 2
 	});
 	await handleReorder(ids);
+	// Clear so the live region does not re-announce on unrelated DOM mutations
+	setTimeout(() => {
+		liveAnnounce = '';
+	}, 500);
 }
 
 async function save(nextStatus: 'DRAFT' | 'PUBLISHED') {
@@ -237,6 +245,7 @@ async function save(nextStatus: 'DRAFT' | 'PUBLISHED') {
 			</p>
 		{/if}
 
+		<!-- pointer events managed by createBlockDragDrop; keyboard reorder available via move-up/down buttons on each item -->
 		<!-- svelte-ignore a11y_no_static_element_interactions -->
 		<div
 			bind:this={listEl}
@@ -248,6 +257,7 @@ async function save(nextStatus: 'DRAFT' | 'PUBLISHED') {
 				<p class="font-sans text-sm text-ink-3">{m.journey_empty_state()}</p>
 			{/if}
 			{#each items as item, i (item.id)}
+				<!-- pointerdown initiates drag; the drag handle button inside is the semantic interactive element -->
 				<!-- svelte-ignore a11y_no_static_element_interactions -->
 				<div
 					data-block-wrapper