Reduce output for LLMs

### Command

build

### Description

Every time Angular builds, it prints chunk stats:

```
Initial chunk files | Names | Raw size | Estimated transfer size
chunk-R3S5GO54.js | - | 269.50 kB | 68.58 kB
chunk-NI535PZY.js | - | 183.41 kB | 55.12 kB
...
```

If you are using an LLM, this unnecessarily reduces available context and eats up tokens.

I couldn't find a flag to disable this output.

### Describe the solution you'd like

Inspired by [this post](https://blog.codemine.be/posts/2026/20260222-be-quiet/), we could support an `LLM` env variable that would drastically reduce the output.

Alternatively a flag to remove stats would be nice.

### Describe alternatives you've considered

`--no-progress`, but it doesn't help.

Start with the build command and the chunk-statistics output described in the issue; verify whether --no-progress affects it. Decide whether an LLM environment variable or a flag is the intended interface, then confirm that the build output omits chunk statistics while preserving the build results.

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