feat: node-specific error tab with selection-aware grouping and error overlay (#8956)

## Summary
Enhances the error panel with node-specific views: single-node selection
shows errors grouped by message in compact mode, container nodes
(subgraph/group) expose child errors via a badge and "See Error" button,
and a floating ErrorOverlay appears after execution failure with a
deduplicated summary and quick navigation to the errors tab.

## Changes
- **Consolidate error tab**: Remove `TabError.vue`; merge all error
display into `TabErrors.vue` and drop the separate `error` tab type from
`rightSidePanelStore`
- **Selection-aware grouping**: Single-node selection regroups errors by
message (not `class_type`) and renders `ErrorNodeCard` in compact mode
- **Container node support**: Detect child-node errors in subgraph/group
nodes via execution ID prefix matching; show error badge and "See Error"
button in `SectionWidgets`
- **ErrorOverlay**: New floating card shown after execution failure with
deduplicated error messages, "Dismiss" and "See Errors" actions;
`isErrorOverlayOpen` / `showErrorOverlay` / `dismissErrorOverlay` added
to `executionStore`
- **Refactor**: Centralize error ID collection in `executionStore`
(`allErrorExecutionIds`, `hasInternalErrorForNode`); split `errorGroups`
into `allErrorGroups` (unfiltered) and `tabErrorGroups`
(selection-filtered); move `ErrorOverlay` business logic into
`useErrorGroups`

## Review Focus
- `useErrorGroups.ts`: split into `allErrorGroups` / `tabErrorGroups`
and the new `filterBySelection` parameter flow
- `executionStore.ts`: `hasInternalErrorForNode` helper and
`allErrorExecutionIds` computed
- `ErrorOverlay.vue`: integration with `executionStore` overlay state
and `useErrorGroups`

## Screenshots
<img width="853" height="461" alt="image"
src="https://github.com/user-attachments/assets/a49ab620-4209-4ae7-b547-fba13da0c633"
/>
<img width="854" height="203" alt="image"
src="https://github.com/user-attachments/assets/c119da54-cd78-4e7a-8b7a-456cfd348f1d"
/>
<img width="497" height="361" alt="image"
src="https://github.com/user-attachments/assets/74b16161-cf45-454b-ae60-24922fe36931"
/>

---------

Co-authored-by: GitHub Action <action@github.com>
Co-authored-by: github-actions <github-actions@github.com>

src/components/error/ErrorOverlay.vue

@@ -0,0 +1,105 @@
+<template>
+  <Transition
+    enter-active-class="transition-all duration-300 ease-out"
+    enter-from-class="-translate-y-3 opacity-0"
+    enter-to-class="translate-y-0 opacity-100"
+  >
+    <div v-if="isVisible" class="flex justify-end w-full pointer-events-none">
+      <div
+        role="alert"
+        aria-live="assertive"
+        data-testid="error-overlay"
+        class="pointer-events-auto flex w-80 min-w-72 flex-col overflow-hidden rounded-lg border border-interface-stroke bg-comfy-menu-bg shadow-interface transition-colors duration-200 ease-in-out"
+      >
+        <!-- Header -->
+        <div class="flex h-12 items-center gap-2 px-4">
+          <span class="flex-1 text-sm font-bold text-destructive-background">
+            {{ errorCountLabel }}
+          </span>
+          <Button
+            variant="muted-textonly"
+            size="icon-sm"
+            :aria-label="t('g.close')"
+            @click="dismiss"
+          >
+            <i class="icon-[lucide--x] block size-5 leading-none" />
+          </Button>
+        </div>
+
+        <!-- Body -->
+        <div class="px-4 pb-3">
+          <ul class="m-0 flex list-none flex-col gap-1.5 p-0">
+            <li
+              v-for="(message, idx) in groupedErrorMessages"
+              :key="idx"
+              class="flex items-baseline gap-2 text-sm leading-snug text-muted-foreground min-w-0"
+            >
+              <span
+                class="mt-1.5 size-1 shrink-0 rounded-full bg-muted-foreground"
+              />
+              <span class="break-words line-clamp-3 whitespace-pre-wrap">{{
+                message
+              }}</span>
+            </li>
+          </ul>
+        </div>
+
+        <!-- Footer -->
+        <div class="flex items-center justify-end gap-4 px-4 py-3">
+          <Button variant="muted-textonly" size="unset" @click="dismiss">
+            {{ t('g.dismiss') }}
+          </Button>
+          <Button variant="secondary" size="lg" @click="seeErrors">
+            {{ t('errorOverlay.seeErrors') }}
+          </Button>
+        </div>
+      </div>
+    </div>
+  </Transition>
+</template>
+
+<script setup lang="ts">
+import { computed, ref } from 'vue'
+import { useI18n } from 'vue-i18n'
+import { storeToRefs } from 'pinia'
+
+import Button from '@/components/ui/button/Button.vue'
+import { useExecutionStore } from '@/stores/executionStore'
+import { useRightSidePanelStore } from '@/stores/workspace/rightSidePanelStore'
+import { useCanvasStore } from '@/renderer/core/canvas/canvasStore'
+import { useErrorGroups } from '@/components/rightSidePanel/errors/useErrorGroups'
+
+const { t } = useI18n()
+const executionStore = useExecutionStore()
+const rightSidePanelStore = useRightSidePanelStore()
+const canvasStore = useCanvasStore()
+
+const { totalErrorCount, isErrorOverlayOpen } = storeToRefs(executionStore)
+const { groupedErrorMessages } = useErrorGroups(ref(''), t)
+
+const errorCountLabel = computed(() =>
+  t(
+    'errorOverlay.errorCount',
+    { count: totalErrorCount.value },
+    totalErrorCount.value
+  )
+)
+
+const isVisible = computed(
+  () => isErrorOverlayOpen.value && totalErrorCount.value > 0
+)
+
+function dismiss() {
+  executionStore.dismissErrorOverlay()
+}
+
+function seeErrors() {
+  if (canvasStore.canvas) {
+    canvasStore.canvas.deselectAll()
+    canvasStore.updateSelectedItems()
+  }
+
+  rightSidePanelStore.openPanel('errors')
+  executionStore.dismissErrorOverlay()
+}
+</script>