Replace analytics grade filter with dual-handle range slider.

Use a single track with min/max thumbs instead of two separate sliders for clearer filtering UX.

src/plugins/built-in/gradeAnalytics/GradeAnalyticsPage.svelte

@@ -10,6 +10,7 @@
   import AnalyticsAreaChart from "./AnalyticsAreaChart.svelte";
   import AnalyticsBarChart from "./AnalyticsBarChart.svelte";
   import AssessmentTable from "./AssessmentTable.svelte";
+  import GradeRangeSlider from "./GradeRangeSlider.svelte";
   import {
     filterAssessmentsByTimeRange,
     getTimeRangeLabel,
@@ -365,13 +366,7 @@
 
       <div class="bsplus-analytics-field bsplus-analytics-grade-range">
         <span class="bsplus-analytics-field-label">Grade range</span>
-        <div class="bsplus-analytics-range-row">
-          <input type="range" min="0" max="100" bind:value={gradeRange[0]} />
-          <input type="range" min="0" max="100" bind:value={gradeRange[1]} />
-          <span class="bsplus-analytics-range-value"
-            >{gradeRange[0]}% – {gradeRange[1]}%</span
-          >
-        </div>
+        <GradeRangeSlider bind:value={gradeRange} />
       </div>
 
       <div class="bsplus-analytics-field bsplus-analytics-toolbar-search">

src/plugins/built-in/gradeAnalytics/GradeRangeSlider.svelte

@@ -0,0 +1,209 @@
+<script lang="ts">
+  let {
+    value = $bindable<[number, number]>([0, 100]),
+    min = 0,
+    max = 100,
+    step = 1,
+  } = $props<{
+    value?: [number, number];
+    min?: number;
+    max?: number;
+    step?: number;
+  }>();
+
+  let dragging: "min" | "max" | null = $state(null);
+
+  const span = $derived(max - min || 1);
+  const minPercent = $derived(((value[0] - min) / span) * 100);
+  const maxPercent = $derived(((value[1] - min) / span) * 100);
+
+  const minZ = $derived(
+    dragging === "min" ? 5 : dragging === "max" ? 2 : value[0] > (min + max) / 2 ? 4 : 3,
+  );
+  const maxZ = $derived(
+    dragging === "max" ? 5 : dragging === "min" ? 2 : value[1] <= (min + max) / 2 ? 4 : 3,
+  );
+
+  function onMinInput(e: Event) {
+    const raw = Number((e.currentTarget as HTMLInputElement).value);
+    if (raw > value[1]) {
+      value = [value[1], raw];
+    } else {
+      value = [raw, value[1]];
+    }
+  }
+
+  function onMaxInput(e: Event) {
+    const raw = Number((e.currentTarget as HTMLInputElement).value);
+    if (raw < value[0]) {
+      value = [raw, value[0]];
+    } else {
+      value = [value[0], raw];
+    }
+  }
+</script>
+
+<div class="bsplus-grade-range-slider">
+  <div class="bsplus-grade-range-slider-track-wrap">
+    <div class="bsplus-grade-range-slider-track" aria-hidden="true">
+      <div class="bsplus-grade-range-slider-rail"></div>
+      <div
+        class="bsplus-grade-range-slider-fill"
+        style:left="{minPercent}%"
+        style:width="{maxPercent - minPercent}%"
+      ></div>
+    </div>
+    <input
+      type="range"
+      class="bsplus-grade-range-slider-input"
+      {min}
+      {max}
+      {step}
+      value={value[0]}
+      oninput={onMinInput}
+      onpointerdown={() => (dragging = "min")}
+      onpointerup={() => (dragging = null)}
+      onpointercancel={() => (dragging = null)}
+      onblur={() => {
+        if (dragging === "min") dragging = null;
+      }}
+      style:z-index={minZ}
+      aria-label="Minimum grade"
+      aria-valuemin={min}
+      aria-valuemax={max}
+      aria-valuenow={value[0]}
+    />
+    <input
+      type="range"
+      class="bsplus-grade-range-slider-input"
+      {min}
+      {max}
+      {step}
+      value={value[1]}
+      oninput={onMaxInput}
+      onpointerdown={() => (dragging = "max")}
+      onpointerup={() => (dragging = null)}
+      onpointercancel={() => (dragging = null)}
+      onblur={() => {
+        if (dragging === "max") dragging = null;
+      }}
+      style:z-index={maxZ}
+      aria-label="Maximum grade"
+      aria-valuemin={min}
+      aria-valuemax={max}
+      aria-valuenow={value[1]}
+    />
+  </div>
+  <span class="bsplus-analytics-range-value" aria-live="polite">
+    {value[0]}% – {value[1]}%
+  </span>
+</div>
+
+<style>
+  .bsplus-grade-range-slider {
+    display: flex;
+    align-items: center;
+    gap: 0.65rem;
+    width: 100%;
+    min-width: 0;
+  }
+
+  .bsplus-grade-range-slider-track-wrap {
+    position: relative;
+    flex: 1;
+    height: 1.5rem;
+    display: flex;
+    align-items: center;
+  }
+
+  .bsplus-grade-range-slider-track {
+    position: absolute;
+    left: 0;
+    right: 0;
+    height: 0.35rem;
+    pointer-events: none;
+  }
+
+  .bsplus-grade-range-slider-rail {
+    position: absolute;
+    inset: 0;
+    border-radius: 999px;
+    background: color-mix(in srgb, var(--bsplus-analytics-muted) 28%, transparent);
+  }
+
+  .bsplus-grade-range-slider-fill {
+    position: absolute;
+    top: 0;
+    bottom: 0;
+    border-radius: 999px;
+    background: var(--bsplus-analytics-accent);
+  }
+
+  .bsplus-grade-range-slider-input {
+    position: absolute;
+    left: 0;
+    width: 100%;
+    margin: 0;
+    height: 1.5rem;
+    background: transparent;
+    pointer-events: none;
+    -webkit-appearance: none;
+    appearance: none;
+    cursor: pointer;
+  }
+
+  .bsplus-grade-range-slider-input::-webkit-slider-runnable-track {
+    -webkit-appearance: none;
+    height: 0.35rem;
+    background: transparent;
+    border: none;
+  }
+
+  .bsplus-grade-range-slider-input::-moz-range-track {
+    height: 0.35rem;
+    background: transparent;
+    border: none;
+  }
+
+  .bsplus-grade-range-slider-input::-webkit-slider-thumb {
+    -webkit-appearance: none;
+    pointer-events: all;
+    width: 1rem;
+    height: 1rem;
+    margin-top: -0.325rem;
+    border-radius: 50%;
+    border: 2px solid var(--bsplus-analytics-accent);
+    background: var(--bsplus-analytics-surface, #fff);
+    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.18);
+    cursor: grab;
+    transition:
+      transform 0.12s var(--bsplus-analytics-ease, ease),
+      box-shadow 0.12s var(--bsplus-analytics-ease, ease);
+  }
+
+  .bsplus-grade-range-slider-input:active::-webkit-slider-thumb {
+    cursor: grabbing;
+    transform: scale(1.08);
+    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.22);
+  }
+
+  .bsplus-grade-range-slider-input::-moz-range-thumb {
+    pointer-events: all;
+    width: 1rem;
+    height: 1rem;
+    border-radius: 50%;
+    border: 2px solid var(--bsplus-analytics-accent);
+    background: var(--bsplus-analytics-surface, #fff);
+    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.18);
+    cursor: grab;
+  }
+
+  .bsplus-grade-range-slider-input:active::-moz-range-thumb {
+    cursor: grabbing;
+    transform: scale(1.08);
+  }
+
+  .bsplus-grade-range-slider :global(.bsplus-analytics-range-value) {
+    flex-shrink: 0;
+  }
+</style>

src/plugins/built-in/gradeAnalytics/styles.css

@@ -402,19 +402,6 @@
   max-width: 20rem;
 }
 
-.bsplus-analytics-range-row {
-  display: flex;
-  align-items: center;
-  gap: 0.65rem;
-}
-
-.bsplus-analytics-range-row input[type="range"] {
-  flex: 1;
-  height: 0.35rem;
-  accent-color: var(--bsplus-analytics-accent);
-  cursor: pointer;
-}
-
 .bsplus-analytics-range-value {
   font-size: 0.75rem;
   font-weight: 600;