Fix copy/paste logic bug in LGraph execution loop (checks onExecute, calls doExecute)

## Recommendation

### 🔧 FIX: Acknowledged Logic Bug

`src/lib/litegraph/src/LGraph.ts:582` contains an acknowledged bug marked with `FIXME`:

> FIXME: Looks like copy/paste broken logic - checks for "on", executes "do"

The conditional checks for `onExecute` but then calls `doExecute`, which appears to be a copy/paste error.

## What Was Found

The graph execution loop has inconsistent logic where the condition checks one method but executes another. This was flagged inline by a developer but never fixed.

## How to Fix

Review the conditional and make it consistent — either check and call `onExecute` or check and call `doExecute`, depending on the intended behavior.

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**Category:** Half-Implemented / Bug | **Priority:** Recommended | **Effort:** Small
Part of #11022
_Filed by repo-audit skill_

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-11070-Fix-copy-paste-logic-bug-in-LGraph-execution-loop-checks-onExecute-calls-doExecute-33e6d73d3650816db1d2f5e6d1ad087b) by [Unito](https://www.unito.io)