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/rightSidePanel/errors/ErrorNodeCard.vue

@@ -1,10 +1,13 @@
 <template>
   <div class="overflow-hidden">
-    <!-- Card Header (Node ID & Actions) -->
-    <div v-if="card.nodeId" class="flex flex-wrap items-center gap-2 py-2">
+    <!-- Card Header -->
+    <div
+      v-if="card.nodeId && !compact"
+      class="flex flex-wrap items-center gap-2 py-2"
+    >
       <span
         v-if="showNodeIdBadge"
-        class="shrink-0 rounded-md bg-secondary-background-selected px-2 py-0.5 text-[10px] font-mono text-muted-foreground font-bold"
+        class="shrink-0 rounded-md bg-secondary-background-selected px-2 py-0.5 text-xs font-mono text-muted-foreground font-bold"
       >
         #{{ card.nodeId }}
       </span>
@@ -19,7 +22,7 @@
         variant="secondary"
         size="sm"
         class="rounded-lg text-sm shrink-0"
-        @click.stop="emit('enterSubgraph', card.nodeId ?? '')"
+        @click.stop="handleEnterSubgraph"
       >
         {{ t('rightSidePanel.enterSubgraph') }}
       </Button>
@@ -27,7 +30,8 @@
         variant="textonly"
         size="icon-sm"
         class="size-7 text-muted-foreground hover:text-base-foreground shrink-0"
-        @click.stop="emit('locateNode', card.nodeId ?? '')"
+        :aria-label="t('rightSidePanel.locateNode')"
+        @click.stop="handleLocateNode"
       >
         <i class="icon-[lucide--locate] size-3.5" />
       </Button>
@@ -43,8 +47,8 @@
       >
         <!-- Error Message -->
         <p
-          v-if="error.message"
-          class="m-0 text-sm break-words whitespace-pre-wrap leading-relaxed px-0.5"
+          v-if="error.message && !compact"
+          class="m-0 text-sm break-words whitespace-pre-wrap leading-relaxed px-0.5 max-h-[4lh] overflow-y-auto"
         >
           {{ error.message }}
         </p>
@@ -69,7 +73,7 @@
         <Button
           variant="secondary"
           size="sm"
-          class="w-full justify-center gap-2 h-8 text-[11px]"
+          class="w-full justify-center gap-2 h-8 text-xs"
           @click="handleCopyError(error)"
         >
           <i class="icon-[lucide--copy] size-3.5" />
@@ -88,9 +92,15 @@ import { cn } from '@/utils/tailwindUtil'
 
 import type { ErrorCardData, ErrorItem } from './types'
 
-const { card, showNodeIdBadge = false } = defineProps<{
+const {
+  card,
+  showNodeIdBadge = false,
+  compact = false
+} = defineProps<{
   card: ErrorCardData
   showNodeIdBadge?: boolean
+  /** Hide card header and error message (used in single-node selection mode) */
+  compact?: boolean
 }>()
 
 const emit = defineEmits<{
@@ -101,6 +111,18 @@ const emit = defineEmits<{
 
 const { t } = useI18n()
 
+function handleLocateNode() {
+  if (card.nodeId) {
+    emit('locateNode', card.nodeId)
+  }
+}
+
+function handleEnterSubgraph() {
+  if (card.nodeId) {
+    emit('enterSubgraph', card.nodeId)
+  }
+}
+
 function handleCopyError(error: ErrorItem) {
   emit(
     'copyToClipboard',