feat: Phase 2 card interactions - priority picker, context menu, WIP limits, column collapse, checklist reorder

- PriorityPicker component with 5 colored chips in card detail modal
- Card context menu: Move to column, Set priority, Duplicate, Delete
- duplicateCard store action (clones card, inserts after original)
- Column WIP limits with amber/red indicators when at/over limit
- Column collapse/expand to 40px vertical strip
- Checklist item drag reordering with grip handle
- Comment store actions (addComment, deleteComment) for Phase 3

src/components/card-detail/PriorityPicker.tsx

@@ -0,0 +1,46 @@
+import { useBoardStore } from "@/stores/board-store";
+import type { Priority } from "@/types/board";
+
+const PRIORITIES: { value: Priority; label: string; color: string }[] = [
+  { value: "none", label: "None", color: "oklch(50% 0 0 / 30%)" },
+  { value: "low", label: "Low", color: "oklch(60% 0.15 240)" },
+  { value: "medium", label: "Medium", color: "oklch(70% 0.15 85)" },
+  { value: "high", label: "High", color: "oklch(60% 0.15 55)" },
+  { value: "urgent", label: "Urgent", color: "oklch(55% 0.15 25)" },
+];
+
+interface PriorityPickerProps {
+  cardId: string;
+  priority: Priority;
+}
+
+export function PriorityPicker({ cardId, priority }: PriorityPickerProps) {
+  const updateCard = useBoardStore((s) => s.updateCard);
+
+  return (
+    <div className="flex flex-col gap-2">
+      <h4 className="font-mono text-xs uppercase tracking-widest text-pylon-text-secondary">
+        Priority
+      </h4>
+      <div className="flex flex-wrap gap-1.5">
+        {PRIORITIES.map(({ value, label, color }) => (
+          <button
+            key={value}
+            onClick={() => updateCard(cardId, { priority: value })}
+            className={`rounded-full px-3 py-1 text-xs font-medium transition-all ${
+              priority === value
+                ? "text-white shadow-sm"
+                : "text-pylon-text-secondary hover:text-pylon-text"
+            }`}
+            style={{
+              backgroundColor: priority === value ? color : undefined,
+              border: priority !== value ? `1px solid ${color}` : `1px solid transparent`,
+            }}
+          >
+            {label}
+          </button>
+        ))}
+      </div>
+    </div>
+  );
+}