fix(admissions): stop 100% trend point being clipped at chart top

A first-choice offer rate sitting on the y-max ceiling (100%) was drawn
flush against the top of the plot area, clipping the point marker. Add 8px
top layout padding and clip:false so ceiling values render in full, without
introducing a misleading >100% tick.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

mockups/admissions-chartjs-check.html

@@ -50,7 +50,7 @@
   new Chart(document.getElementById('c'),{
     type:'line',
     data:{labels,datasets:[{
-      label:'First-choice offer rate',data:values,
+      label:'First-choice offer rate',data:values,clip:false,
       borderColor:'#e07256',backgroundColor:'rgba(224,114,86,0.10)',
       borderWidth:2.5,tension:0.3,fill:true,
       pointRadius:values.map((_,i)=>i===lastIdx?5:3),
@@ -59,6 +59,7 @@
     }]},
     options:{
       responsive:true,maintainAspectRatio:false,
+      layout:{padding:{top:8}},
       interaction:{mode:'index',intersect:false},
       plugins:{legend:{display:false},title:{display:false},
         tooltip:{backgroundColor:'rgba(26,22,18,0.92)',padding:10,callbacks:{label:ctx=>`First-choice offers: ${Math.round(ctx.parsed.y)}%`}}},