fix(scripts): stop hiding build failures in the setup scripts

`prepare.sh` and `run-integration.sh` sent the build output to /dev/null and had no
shebang, no `set -e` and no exit status check. A failed build was invisible, the script
carried on into the Docker steps and still exited 0.

The `&>` redirect was also not portable. Under dash, which is /bin/sh on most Debian and
Ubuntu systems, it parses as "run in the background" plus a separate no-op redirect, so
the build raced the steps that followed instead of being muted.

Adds `#!/usr/bin/env bash` and `set -eu` to both scripts and drops the redirect.
`pipefail` is left out on purpose so the scripts still work when invoked with `sh` on a
dash system; neither script uses a pipeline and neither reads a shell variable.

Also corrects CONTRIBUTING.md. `npm run build` runs `move:node_modules`, which copies the
compiled output into the root `node_modules/@nestjs`; `move:samples` is a separate task
that only `build:samples` invokes. Two places claimed the build moves packages into the
`sample` directories. `prepare.sh` also starts Docker containers and waits for RabbitMQ,
which its description did not mention, and `npm run test` needs neither a build nor
Docker, so it now comes before the integration setup.

CONTRIBUTING.md

@@ -166,18 +166,30 @@ You will need [Node.js](https://nodejs.org) version >= 20.
 $ npm ci --legacy-peer-deps # (or yarn install)
 ```
 
-2. In order to prepare your environment run `prepare.sh` shell script:
+2. To run the unit tests you are ready to go:
 
 ```bash
-$ sh scripts/prepare.sh
+$ npm run test
 ```
 
-That will compile fresh packages and afterward, move them all to `sample` directories.
+The unit tests run straight from the TypeScript sources, so no build step and no Docker
+are required.
+
+3. Only if you are going to run the **integration** tests, prepare that environment with
+   the `prepare.sh` shell script:
+
+```bash
+$ bash scripts/prepare.sh
+```
+
+That will compile fresh packages into the root `node_modules/@nestjs`, then start the
+Docker containers the integration tests need and wait for RabbitMQ to accept
+connections. Docker is required for this step.
 
 ### <a name="common-scripts"></a>Commonly used NPM scripts
 
 ```bash
-# build all packages and move to "sample" directories
+# build all packages into the root node_modules/@nestjs
 $ npm run build
 
 # run the full unit tests suite
@@ -185,7 +197,7 @@ $ npm run test
 
 # run integration tests
 # docker is required(!)
-$ sh scripts/run-integration.sh
+$ bash scripts/run-integration.sh
 
 # run linter
 $ npm run lint

scripts/prepare.sh

@@ -1,5 +1,8 @@
+#!/usr/bin/env bash
+set -eu
+
 # 1. Build fresh packages and move them to sample and integration directories
-npm run build &>/dev/null
+npm run build
 
 # 2. Start docker containers to perform integration tests
 npm run test:docker:up

scripts/run-integration.sh

@@ -1,5 +1,8 @@
-# 1. Build fresh packages and move them integration dit
-npm run build &>/dev/null
+#!/usr/bin/env bash
+set -eu
+
+# 1. Build fresh packages and move them to the integration directory
+npm run build
 
 # 2. Start docker containers to perform integration tests
 npm run test:docker:up