Write an environment recipe

This guide writes the environment recipe: the image, the install steps and the test commands that every case of a workspace runs with. Casebox builds the recipe once per workspace, and a person confirms it.

Draft it from what the repository has:
Terminal window
```
casebox env draft
```
The draft reads devcontainer.json, Dockerfiles, compose files and CI workflows. It prints an environment: block with the source of each field as a comment.

Edit the block into casebox.yml:

environment:
  image: golang:1.26
  lockfiles: [go.sum]
  install: ["go mod download"]
  test:
    - command: go test -json ./...
      results: go-test-json
      timeout: 10m
  services:
    postgres: { image: "postgres:16", env: { POSTGRES_PASSWORD: test } }

Build it and run the tests at HEAD:
Terminal window
```
casebox env check
```
The report says what passed, failed or timed out. A test that fetches from the network at run time shows here: sealed runs block the network, so fix it before you confirm.
Confirm it:
Terminal window
```
casebox env confirm
```

Rules for a good recipe:

Name a results format for each test command: go-test-json, trx or junit. Without one, Casebox counts only the exit code, so no case can prove that its change did the work.
List the lockfiles. Their content keys the image cache, so a changed lockfile rebuilds the image and an unchanged one reuses it.
Keep services in compose form. Each run gets its own services on a private network.