Update README and vector assets

modules/story-summary/story-summary.css

@@ -178,12 +178,11 @@ h1 span {
 }
 
 #keep-visible-count {
-    width: 3ch;         /* 可稳定显示 3 位数字：0-50 足够 */
-    min-width: 3ch;
-    max-width: 4ch;
-    font-variant-numeric: tabular-nums;
-    padding: 2px 4px;
-    margin: 0 2px;
+    width: 3.5em;
+    min-width: 3em;
+    max-width: 4em;
+    padding: 4px 6px;
+    margin: 0 4px;
     background: var(--bg2);
     border: 1px solid var(--bdr);
     font-size: inherit;
@@ -191,6 +190,17 @@ h1 span {
     color: var(--hl);
     text-align: center;
     border-radius: 3px;
+    font-variant-numeric: tabular-nums;
+
+    /* 禁用 number input 的 spinner（PC 上会挤掉数字） */
+    -moz-appearance: textfield;
+    appearance: textfield;
+}
+
+#keep-visible-count::-webkit-outer-spin-button,
+#keep-visible-count::-webkit-inner-spin-button {
+    -webkit-appearance: none;
+    margin: 0;
 }
 
 #keep-visible-count:focus {