fix: use Svelte action for contenteditable to prevent cursor destruction

The reactive {#html} binding inside contenteditable replaced innerHTML on
every keystroke, destroying the cursor and causing text duplication.

Instead, use a use:editableContent action that sets innerHTML on mount
and only syncs when the element is NOT focused. Linkification happens
on blur, matching Google Keep's behavior. Update e2e tests to blur
before asserting link visibility.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/lib/components/Checklist.svelte

@@ -157,6 +157,20 @@
 		}
 	}
 
+	// Svelte action: sets innerHTML on mount and syncs from external changes only.
+	// While the user is typing (element is focused), we don't re-render — that would
+	// destroy the cursor. Linkification happens on blur via the onblur handler.
+	function editableContent(node: HTMLElement, text: string) {
+		node.innerHTML = linkifyText(text);
+		return {
+			update(newText: string) {
+				if (document.activeElement !== node) {
+					node.innerHTML = linkifyText(newText);
+				}
+			}
+		};
+	}
+
 	function handleLinkClick(e: MouseEvent) {
 		const target = e.target as HTMLElement;
 		const anchor = target.closest('a');
@@ -305,17 +319,19 @@
 				<!-- svelte-ignore a11y_no_static_element_interactions -->
 				<div
 					contenteditable="true"
+					use:editableContent={item.text}
 					oninput={(e) => updateText(item.id, (e.target as HTMLElement).innerHTML)}
 					onkeydown={(e) => handleKeydown(e, item.id)}
 					onclick={handleLinkClick}
 					onpaste={handlePaste}
+					onblur={(e) => { (e.target as HTMLElement).innerHTML = linkifyText(item.text); }}
 					class="flex-1 min-w-0 bg-transparent text-sm outline-none break-words {item.checked ? 'text-[var(--text-muted)] line-through' : 'text-[var(--text)]'}"
 					data-placeholder="List item"
 					data-testid="checklist-input"
 					data-item-id={item.id}
 					role="textbox"
 					tabindex="0"
-				>{@html linkifyText(item.text)}</div>
+				></div>
 				<button
 					onclick={() => removeItem(item.id)}
 					class="max-md:opacity-100 md:opacity-0 md:group-hover:opacity-100 focus:opacity-100"