fix(variety): remove unused total, add warning border, fix abbreviation, aria

- EffortBar: remove unused \`total\` derived variable
- VarietyWarningCards: add border border-[var(--yellow-light)] to cards
- variety page: protein abbreviation uses split(' ')[0].slice(0,3).toUpperCase()
- variety page: breadcrumb separator span gets aria-hidden="true"

Addresses Kai blocker: unused total. Atlas blockers: yellow-light border,
protein abbreviation, breadcrumb aria.

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

frontend/src/lib/planner/EffortBar.svelte

@@ -9,7 +9,7 @@
 		hard: number;
 	} = $props();
 
-	let total = $derived(easy + medium + hard);
+
 </script>
 
 <!-- Labels below the bar -->