ng serve with @angular/build: DevTools file search not working

### Command

serve

### Is this a regression?

- [x] Yes, this behavior used to work in the previous version

### The previous version in which this bug was not present was

angular19 with @angular-devkit/build-angular

### Description

When I try to migrate an Angular 20 project from @angular-devkit/build-angular to the new @angular/build, I notice that when running `ng serve` and opening the browser DevTools → Sources, searching for content across all files does not return any results.

### Minimal Reproduction

Angular versions: 20, 21, and 22 (out of the box)
Browser: Edge and Chrome
Operating System: Windows and Linux
SSR: off
Zoneless: off

Steps:
1. Create a new Angular app with `ng new v20`.
2. Run `ng serve`.
3. Open the browser and go to DevTools → Sources.
4. Try to search for content across all files.

Steps:
1. Create a new Angular app with `ng new v22`.
2. Run `ng serve`.
3. Open the browser and go to DevTools → Sources.
4. Try to search for content across all files.

### Exception or Error

```text

```

### Your Environment

```text
Angular CLI: 20.3.31
Node: 22.14.0
Package Manager: npm 10.9.2
OS: linux x64

Angular: 20.3.25
... common, compiler, compiler-cli, core, forms
... platform-browser, router

Package Version
------------------------------------
@angular-devkit/architect 0.2003.31
@angular-devkit/core 20.3.31
@angular-devkit/schematics 20.3.31
@angular/build 20.3.31
@angular/cli 20.3.31
@schematics/angular 20.3.31
rxjs 7.8.2
typescript 5.9.3
zone.js 0.15.1

---------------------------------------

Angular CLI : 22.0.5
Angular : 22.0.5
Node.js : 24.18.0
Package Manager : npm 11.16.0
Operating System : linux x64

┌───────────────────────────┬───────────────────┬───────────────────┐
│ Package │ Installed Version │ Requested Version │
├───────────────────────────┼───────────────────┼───────────────────┤
│ @angular/build │ 22.0.5 │ ^22.0.5 │
│ @angular/cli │ 22.0.5 │ ^22.0.5 │
│ @angular/common │ 22.0.5 │ ^22.0.0 │
│ @angular/compiler │ 22.0.5 │ ^22.0.0 │
│ @angular/compiler-cli │ 22.0.5 │ ^22.0.0 │
│ @angular/core │ 22.0.5 │ ^22.0.0 │
│ @angular/forms │ 22.0.5 │ ^22.0.0 │
│ @angular/platform-browser │ 22.0.5 │ ^22.0.0 │
│ @angular/router │ 22.0.5 │ ^22.0.0 │
│ rxjs │ 7.8.2 │ ~7.8.0 │
│ typescript │ 6.0.3 │ ~6.0.2 │
│ vitest │ 4.1.9 │ ^4.0.8 │
└───────────────────────────┴───────────────────┴───────────────────┘
```

### Anything else relevant?

Angula version: 19 (out of the box)
Browser: Edge and Chrome
Operating System: Windows and Linux
SSR: off

Steps:
1. Create a new Angular app with `ng new v19`.
2. Run `ng serve`.
3. Open the browser and go to DevTools → Sources.
4. Try to search for content across all files.

Result:
The search works correctly in Angular 19.

Angular CLI: 19.2.27
Node: 22.14.0
Package Manager: npm 10.9.2
OS: linux x64

Angular: 19.2.25
... common, compiler, compiler-cli, core, forms
... platform-browser, platform-browser-dynamic, router

Package Version
---------------------------------------------------------
@angular-devkit/architect 0.1902.27
@angular-devkit/build-angular 19.2.27
@angular-devkit/core 19.2.27
@angular-devkit/schematics 19.2.27
@angular/cli 19.2.27
@schematics/angular 19.2.27
rxjs 7.8.2
typescript 5.7.3
zone.js 0.15.1

Tái hiện sự cố với một ứng dụng Angular mới bằng cách sử dụng `ng serve` và `@angular/build`, sau đó so sánh với Angular 19 bằng cách sử dụng `@angular-devkit/build-angular`. Kiểm tra cách đầu ra của serve được hiển thị trong Chrome hoặc Edge DevTools Sources. Được xem là hoàn tất khi tìm kiếm xuyên tệp trả về nội dung trong Angular 20+ giống như trong Angular 19 và hồi quy liên quan được các bài kiểm thử của dự án bao phủ.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.