feat: add BaseTooltip component using Reka UI

Add foundational tooltip component with three variants (default, small,
large), four positioning sides, and configurable delay/disabled state.
Wrap App.vue in TooltipProvider for app-wide tooltip support. Include
Storybook stories for all variants, sides, disabled, and long text.

src/components/ui/tooltip/BaseTooltip.vue

@@ -0,0 +1,56 @@
+<script setup lang="ts">
+import type { HTMLAttributes } from 'vue'
+
+import {
+  TooltipArrow,
+  TooltipContent,
+  TooltipPortal,
+  TooltipRoot,
+  TooltipTrigger
+} from 'reka-ui'
+
+import type { TooltipVariants } from '@/components/ui/tooltip/tooltip.variants'
+import { tooltipVariants } from '@/components/ui/tooltip/tooltip.variants'
+import { cn } from '@/utils/tailwindUtil'
+
+const {
+  text = '',
+  side = 'top',
+  sideOffset = 4,
+  variant = 'default',
+  delayDuration,
+  disabled = false,
+  class: className
+} = defineProps<{
+  text?: string
+  side?: 'top' | 'bottom' | 'left' | 'right'
+  sideOffset?: number
+  variant?: NonNullable<TooltipVariants['variant']>
+  delayDuration?: number
+  disabled?: boolean
+  class?: HTMLAttributes['class']
+}>()
+</script>
+
+<template>
+  <TooltipRoot :delay-duration="delayDuration" :disabled="disabled || !text">
+    <TooltipTrigger as-child>
+      <slot />
+    </TooltipTrigger>
+    <TooltipPortal>
+      <TooltipContent
+        :side="side"
+        :side-offset="sideOffset"
+        :class="cn(tooltipVariants({ variant }), className)"
+      >
+        {{ text }}
+        <TooltipArrow
+          v-if="variant !== 'default'"
+          :width="8"
+          :height="5"
+          class="fill-node-component-tooltip-surface"
+        />
+      </TooltipContent>
+    </TooltipPortal>
+  </TooltipRoot>
+</template>