feat: add SpeedSelector popup component

Co-authored-by: Cursor <cursoragent@cursor.com>

src/lib/components/SpeedSelector.svelte

@@ -0,0 +1,89 @@
+<script lang="ts">
+  const SPEED_OPTIONS = [0.5, 0.75, 1, 1.25, 1.5, 2] as const;
+
+  let {
+    currentRate,
+    onSelect,
+    onClose,
+  }: {
+    currentRate: number;
+    onSelect: (rate: number) => void;
+    onClose: () => void;
+  } = $props();
+
+  function handleSelect(rate: number) {
+    onSelect(rate);
+    onClose();
+  }
+
+  function handleWindowClick(e: MouseEvent) {
+    const target = e.target as HTMLElement;
+    if (!target.closest('.speed-selector')) {
+      onClose();
+    }
+  }
+</script>
+
+<svelte:window onclick={handleWindowClick} />
+
+<div class="speed-selector" role="menu">
+  {#each SPEED_OPTIONS as rate (rate)}
+    <button
+      class="speed-option"
+      class:active={Math.abs(currentRate - rate) < 0.01}
+      role="menuitem"
+      onclick={() => handleSelect(rate)}
+    >
+      <span class="check">{Math.abs(currentRate - rate) < 0.01 ? '✓' : ''}</span>
+      {rate}×
+    </button>
+  {/each}
+</div>
+
+<style>
+  .speed-selector {
+    position: absolute;
+    bottom: 100%;
+    right: 0;
+    margin-bottom: 8px;
+    background: rgba(0, 0, 0, 0.85);
+    backdrop-filter: blur(8px);
+    border-radius: 8px;
+    padding: 4px;
+    display: flex;
+    flex-direction: column;
+    min-width: 80px;
+    z-index: 50;
+    border: 1px solid rgba(255, 255, 255, 0.1);
+  }
+
+  .speed-option {
+    display: flex;
+    align-items: center;
+    gap: 6px;
+    padding: 6px 12px;
+    background: transparent;
+    border: none;
+    color: var(--text-primary, #cdd6f4);
+    font-size: 13px;
+    cursor: pointer;
+    border-radius: 4px;
+    white-space: nowrap;
+  }
+
+  .speed-option:hover {
+    background: rgba(255, 255, 255, 0.1);
+    color: var(--accent, #89b4fa);
+  }
+
+  .speed-option.active {
+    color: var(--accent, #89b4fa);
+    font-weight: 600;
+  }
+
+  .check {
+    width: 14px;
+    font-size: 11px;
+    text-align: center;
+  }
+</style>