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/core/graph/subgraph/matchPromotedInput.test.ts

@@ -0,0 +1,77 @@
+import { describe, expect, it } from 'vitest'
+
+import type { IBaseWidget } from '@/lib/litegraph/src/types/widgets'
+
+import { matchPromotedInput } from './matchPromotedInput'
+
+type MockInput = {
+  name: string
+  _widget?: IBaseWidget
+}
+
+function createWidget(name: string): IBaseWidget {
+  return {
+    name,
+    type: 'text'
+  } as IBaseWidget
+}
+
+describe(matchPromotedInput, () => {
+  it('prefers exact _widget matches before same-name inputs', () => {
+    const targetWidget = createWidget('seed')
+    const aliasWidget = createWidget('seed')
+
+    const aliasInput: MockInput = {
+      name: 'seed',
+      _widget: aliasWidget
+    }
+    const exactInput: MockInput = {
+      name: 'seed',
+      _widget: targetWidget
+    }
+
+    const matched = matchPromotedInput(
+      [aliasInput, exactInput] as unknown as Array<{
+        name: string
+        _widget?: IBaseWidget
+      }>,
+      targetWidget
+    )
+
+    expect(matched).toBe(exactInput)
+  })
+
+  it('falls back to same-name matching when no exact widget match exists', () => {
+    const targetWidget = createWidget('seed')
+    const aliasInput: MockInput = {
+      name: 'seed'
+    }
+
+    const matched = matchPromotedInput(
+      [aliasInput] as unknown as Array<{ name: string; _widget?: IBaseWidget }>,
+      targetWidget
+    )
+
+    expect(matched).toBe(aliasInput)
+  })
+
+  it('does not guess when multiple same-name inputs exist without an exact match', () => {
+    const targetWidget = createWidget('seed')
+    const firstAliasInput: MockInput = {
+      name: 'seed'
+    }
+    const secondAliasInput: MockInput = {
+      name: 'seed'
+    }
+
+    const matched = matchPromotedInput(
+      [firstAliasInput, secondAliasInput] as unknown as Array<{
+        name: string
+        _widget?: IBaseWidget
+      }>,
+      targetWidget
+    )
+
+    expect(matched).toBeUndefined()
+  })
+})