fix: dashboard "New Idea" button now targets first collection (#95)

The dashboard had two buttons that both called requestQuickAdd() with
no argument, so both created tasks. Now:

- "New Task" explicitly targets the tasks collection
- The second button dynamically targets the first non-system, non-task
  collection by sort order (showing its icon and name)
- requestQuickAdd() accepts an optional collection slug, which the
  sidebar respects when choosing the target collection

Fixes BUG-498.

web/src/lib/components/layout/Sidebar.svelte

@@ -108,8 +108,10 @@
 	// Watch for Cmd-N quick-add requests from the layout
 	$effect(() => {
 		if (uiStore.quickAddRequested) {
+			const targetSlug = uiStore.quickAddTargetSlug;
 			uiStore.clearQuickAddRequest();
-			const target = activeColl
+			const target = (targetSlug ? regularCollections.find(c => c.slug === targetSlug) : null)
+				?? activeColl
 				?? regularCollections.find(c => c.slug === 'tasks')
 				?? regularCollections[0];
 			if (target) startQuickAdd(target);

web/src/lib/stores/ui.svelte.ts

@@ -8,6 +8,7 @@ let isTouch = $state(browser ? 'ontouchstart' in window : false);
 let detailPanelOpen = $state(browser ? localStorage.getItem('pad-detail-panel') !== 'closed' && window.innerWidth > 768 : false);
 let createWorkspaceOpen = $state(false);
 let quickAddRequested = $state(false);
+let quickAddTargetSlug = $state<string | null>(null);
 
 if (browser) {
 	window.addEventListener('resize', () => {
@@ -71,8 +72,9 @@ export const uiStore = {
 
 	// Quick-add item trigger — sidebar watches this
 	get quickAddRequested() { return quickAddRequested; },
-	requestQuickAdd() { quickAddRequested = true; },
-	clearQuickAddRequest() { quickAddRequested = false; },
+	get quickAddTargetSlug() { return quickAddTargetSlug; },
+	requestQuickAdd(collectionSlug?: string) { quickAddTargetSlug = collectionSlug ?? null; quickAddRequested = true; },
+	clearQuickAddRequest() { quickAddRequested = false; quickAddTargetSlug = null; },
 
 	/** Close sidebar on mobile after navigation */
 	onNavigate() {

web/src/routes/[username]/[workspace]/+page.svelte

@@ -78,6 +78,7 @@
 	}
 
 	let totalItems = $derived(dashboard?.summary.total_items ?? 0);
+	let firstCollection = $derived(collections.filter(c => !c.is_system && c.slug !== 'tasks').sort((a, b) => a.sort_order - b.sort_order)[0]);
 
 	function statusColor(status: string): string {
 		const s = status.toLowerCase().replace(/-/g, '_');
@@ -176,8 +177,10 @@
 				<span class="item-count">{totalItems} item{totalItems !== 1 ? 's' : ''}</span>
 			</div>
 			<div class="dash-header-actions">
-				<button class="btn btn-secondary" onclick={() => uiStore.requestQuickAdd()}>💡 New Idea</button>
-				<button class="btn btn-primary" onclick={() => uiStore.requestQuickAdd()}>+ New Task</button>
+				{#if firstCollection}
+					<button class="btn btn-secondary" onclick={() => uiStore.requestQuickAdd(firstCollection.slug)}>{firstCollection.icon} New {firstCollection.name.replace(/s$/, '')}</button>
+				{/if}
+				<button class="btn btn-primary" onclick={() => uiStore.requestQuickAdd('tasks')}>+ New Task</button>
 			</div>
 		</header>