fix(core): ensure local plugin is transpiled when using index files (#30133)

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## Current Behavior
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In some use cases the local plugins generators and executors are not
transpiled, which causes an error when you execute them. see for example
![Screenshot 2025-02-21 at 09 07
10](https://github.com/user-attachments/assets/1fd03a4b-1ac4-4827-b240-b4ea88d491a2)

This issue is introduced by this PR #29539 and is actually a regression
of an error we had in NX 18, see #22958

## Expected Behavior
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-->
This PR fixes this issue by updating the if statement to register the
typescript transpiler when this is not done yet.

## Related Issue(s)
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merged. -->

Fixes #30132

Author: Roozenboom

packages/nx/src/project-graph/plugins/in-process-loader.ts

@@ -42,7 +42,7 @@ export function readPluginPackageJson(
           localPluginPath.path,
           'package.json'
         );
-        if (pluginTranspilerIsRegistered()) {
+        if (!pluginTranspilerIsRegistered()) {
           registerPluginTSTranspiler();
         }
         return {