Which @angular/* package(s) are the source of the bug?

core

Is this a regression?

No

Description

In multi-project workspace, the inject migration doesn't work when targeting one of the projects due to either not finding any files in other projects or considering them external thus it throws a SchematicsException

Minimal Reproduction

1. Create a new workspace with Angular CLI
   a. ng new my-workspace --no-create-application
2. Generate a new application in the workspace
   a. ng generate application my-app
3. Generate a new library in the workspace
   a. ng generate library my-lib
4. Create a new service
5. Import service into generated component in my-lib
6. Run inject migration targeting the library
   a. ng generate @angular/core:inject --path=./projects/my-lib/src

Please provide a link to a minimal reproduction of the bug

https://stackblitz.com/edit/stackblitz-starters-ap2u31fu

Please provide the exception or error you saw

`Could not find any files to migrate under the path \\home\\projects\\stackblitz-starters-ap2u31fu\\projects\\my-lib\\src. Cannot run the inject migration.`

Please provide the environment you discovered this bug in (run ng version)

Angular CLI       : 21.0.3
Angular           : 21.0.5
Node.js           : 20.19.1
Package Manager   : npm 10.8.2
Operating System  : linux x64

 
Package				Version
------------------------------------------------
@angular/build			 21.0.3
@angular/cli			 21.0.3
@angular/common			 21.0.5
@angular/compiler		 21.0.5
@angular/compiler-cli		 21.0.5
@angular/core			 21.0.5
@angular/forms			 21.0.5
@angular/platform-browser	 21.0.5
@angular/router			 21.0.5
ng-packagr			 21.0.0
rxjs				 7.8.2
typescript			 5.9.3
vitest				 4.0.15

Anything else?

I couldn't find any information if this multi-project scenario are supported by migrations so I'm not sure if this is a bug or not.

One thing I noticed is that in the source code the exception is thrown if no files are found, so maybe a naïve fix could be just rendering a warning but continue to the next tsconfig file so that the whole migration process isn't interrupted (however it might still ignores due to the external library check)

Alternatives considered

In a similar but now deprecated migration made by @eneajaho in the ngxtension project it contains a --project flag which could be a nice solution
https://ngxtension.dev/utilities/migrations/inject-migration/#options