fix: stabilize subgraph promoted widget identity and rendering (#9896)

## Summary

Fix subgraph promoted widget identity/rendering so on-node widgets stay
correct through configure/hydration churn, duplicate names, and
linked+independent coexistence.

## Changes

- **Subgraph promotion reconciliation**: stabilize linked-entry identity
by subgraph slot id, preserve deterministic linked representative
selection, and prune stale alias/fallback entries without dropping
legitimate independent promotions.
- **Promoted view resolution**: bind slot mapping by promoted view
object identity (`getSlotFromWidget` / `getWidgetFromSlot`) to avoid
same-name collisions.
- **On-node widget rendering**: harden `NodeWidgets` identity and dedup
to avoid visual aliasing, prefer visible duplicates over hidden stale
entries, include type/source execution identity, and avoid collapsing
transient unresolved entries.
- **Mapping correctness**: update `useGraphNodeManager` promoted source
mapping to resolve by input target only when the promoted view is
actually bound to that input.
- **Subgraph input uniqueness**: ensure empty-slot promotion creates
unique input names (`seed`, `seed_1`, etc.) for same-name multi-source
promotions.
- **Safety fix**: guard against undefined canvas in slot-link
interaction.
- **Tests/fixtures**: add focused regressions for fixture path
`subgraph_complex_promotion_1`, linked+independent same-name cases,
duplicate-name identity mapping, dedup behavior, and input-name
uniqueness.

## Review Focus

Validate behavior around transient configure/hydration states (`-1` id
to concrete id), duplicate-name promotions, linked representative
recovery, and that dedup never hides legitimate widgets while still
removing true duplicates.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9896-fix-stabilize-subgraph-promoted-widget-identity-and-rendering-3226d73d365081c8a1e8d0a5a22e826d)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Amp <amp@ampcode.com>

src/composables/graph/useGraphNodeManager.ts

@@ -7,6 +7,7 @@ import { reactive, shallowReactive } from 'vue'
 
 import { useChainCallback } from '@/composables/functional/useChainCallback'
 import { isPromotedWidgetView } from '@/core/graph/subgraph/promotedWidgetTypes'
+import { matchPromotedInput } from '@/core/graph/subgraph/matchPromotedInput'
 import { resolveConcretePromotedWidget } from '@/core/graph/subgraph/resolveConcretePromotedWidget'
 import { resolvePromotedWidgetSource } from '@/core/graph/subgraph/resolvePromotedWidgetSource'
 import { resolveSubgraphInputTarget } from '@/core/graph/subgraph/resolveSubgraphInputTarget'
@@ -244,16 +245,17 @@ function safeWidgetMapper(
       }
     }
 
-    const promotedInputName = node.inputs?.find((input) => {
-      if (input.name === widget.name) return true
-      if (input._widget === widget) return true
-      return false
-    })?.name
+    const matchedInput = matchPromotedInput(node.inputs, widget)
+    const promotedInputName = matchedInput?.name
     const displayName = promotedInputName ?? widget.name
-    const promotedSource = resolvePromotedSourceByInputName(displayName) ?? {
+    const directSource = {
       sourceNodeId: widget.sourceNodeId,
       sourceWidgetName: widget.sourceWidgetName
     }
+    const promotedSource =
+      matchedInput?._widget === widget
+        ? (resolvePromotedSourceByInputName(displayName) ?? directSource)
+        : directSource
 
     return {
       displayName,