Adopt shared WebUI layout primitives

webui/src/features/cases/CaseDecisionDialog.tsx

@@ -1,6 +1,6 @@
 import { Scale } from "lucide-react";
 import { useEffect, useMemo, useRef, useState } from "react";
-import {
+import { FormGrid,
   Button,
   ConfirmDialog,
   Dialog,
@@ -125,7 +125,7 @@ export default function CaseDecisionDialog({
           <p className="case-decision-explanation">
             The server verifies your current acting assignment, the effective Mandate, the exact Case revision, evidence, and legal basis before recording the outcome.
           </p>
-          <div className="case-decision-grid">
+          <FormGrid columns={2} gap="small" collapseAt="workspace" className="case-decision-grid">
             <FormField label="Decision type" documentation={CASES_FIELDS_DOCUMENTATION}>
               <input
                 value={decisionType}
@@ -142,7 +142,7 @@ export default function CaseDecisionDialog({
                 onChange={(event) => setEffectiveAt(event.target.value)}
               />
             </FormField>
-          </div>
+          </FormGrid>
           <FormField label="Operative result" documentation={CASES_FIELDS_DOCUMENTATION}>
             <textarea
               rows={4}