Fiks BlockShell-knapper: stopPropagation forhindrer drag-capture

Minimer, maksimer og lukk-knapper ble fanget av header-dragging
pga setPointerCapture. Nå: stopPropagation på controls-div og
individuelle knapper, pluss .closest('.blockshell-controls') sjekk.

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

frontend/src/lib/components/blockshell/BlockShell.svelte

@@ -142,9 +142,10 @@
 
 	// --- Drag (repositioning via header) ---
 	function handleDragStart(e: PointerEvent) {
-		// Only left button, not on buttons
+		// Only left button, not on buttons or controls
 		if (e.button !== 0) return;
 		if ((e.target as HTMLElement).closest('button')) return;
+		if ((e.target as HTMLElement).closest('.blockshell-controls')) return;
 
 		isDragging = true;
 		hasDragged = false;
@@ -351,11 +352,12 @@
 			<span class="blockshell-title">{title}</span>
 		</div>
 
-		<div class="blockshell-controls">
+		<!-- svelte-ignore a11y_no_static_element_interactions -->
+		<div class="blockshell-controls" onpointerdown={(e) => e.stopPropagation()}>
 			{#if !isFullscreen}
 				<button
 					class="blockshell-btn"
-					onclick={() => onMinimizeChange?.(!minimized)}
+					onclick={(e) => { e.stopPropagation(); onMinimizeChange?.(!minimized); }}
 					title={minimized ? 'Gjenopprett' : 'Minimer'}
 					aria-label={minimized ? 'Gjenopprett panel' : 'Minimer panel'}
 				>
@@ -364,7 +366,7 @@
 			{/if}
 			<button
 				class="blockshell-btn"
-				onclick={toggleFullscreen}
+				onclick={(e) => { e.stopPropagation(); toggleFullscreen(); }}
 				title={isFullscreen ? 'Avslutt fullskjerm' : 'Fullskjerm'}
 				aria-label={isFullscreen ? 'Avslutt fullskjerm' : 'Fullskjerm'}
 			>
@@ -373,7 +375,7 @@
 			{#if closable}
 				<button
 					class="blockshell-btn blockshell-btn-close"
-					onclick={() => onClose?.()}
+					onclick={(e) => { e.stopPropagation(); onClose?.(); }}
 					title="Lukk"
 					aria-label="Lukk panel"
 				>