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.

索引モデルが issue の本文から書いたものです。