`sls-offline-authorizer-override` header and `AUTHORIZER` env var do not populate `event.requestContext.authorizer` when using `request`-type custom authorizer

## Bug Report

**Current Behavior**

The `sls-offline-authorizer-override` custom header and the `AUTHORIZER` environment variable both fail to populate `event.requestContext.authorizer` regardless of the `noAuth` setting in `serverless.yml`.

- With `noAuth: true`: the header `sls-offline-authorizer-override` is received but ends up in `event.headers` instead of `event.requestContext.authorizer`. The authorizer context is filled with `offlineContext_*` defaults, ignoring the override entirely.
- With `noAuth: false`: the server returns `401` because the real authorizer is invoked, making local development without valid credentials impossible.
- The `AUTHORIZER` env var (documented as a way to mock remote authorizers) also has no effect, as reported in #1826.

This makes it impossible to test functions locally that depend on `event.requestContext.authorizer` values without resorting to workarounds.

**Sample Code**

- file: `serverless.yml`

```yaml
service: my-service

plugins:
- serverless-offline

provider:
name: aws
runtime: nodejs20.x
stage: dev

functions:
myAuthorizer:
handler: functions/authorizer.main
timeout: 200

hello:
handler: functions/hello.main
events:
- http:
path: /hello/{id}
method: get
authorizer:
name: myAuthorizer
identitySource: method.request.header.Authorization
resultTtlInSeconds: 0
type: request

custom:
serverless-offline:
noAuth: true
noTimeout: true
```

- file: `functions/hello.js`

```js
exports.main = async (event) => {
const allowCpf = event.requestContext.authorizer.allowCpf
if (!allowCpf) return { statusCode: 400, body: JSON.stringify({ error: 'allowCpf missing' }) }

return {
statusCode: 200,
body: JSON.stringify({ allowCpf }),
}
}
```

Request made with:

```bash
curl http://localhost:3000/dev/hello/123 \
--header 'sls-offline-authorizer-override: {"allowCpf": "12345678900"}'
```

**Expected behavior**

`event.requestContext.authorizer` should be `{ allowCpf: "12345678900" }` as set via the `sls-offline-authorizer-override` header.

**Actual behavior**

`event.requestContext.authorizer` contains only `offlineContext_*` defaults. The override header is present in `event.headers` but never applied to the authorizer context.

**Environment**

- `serverless` version: 3.40.0
- `serverless-offline` version: 7.2.3
- `node.js` version: 24.14.1
- `OS`: Windows 11

**Additional context**

Related to #1826, which reports the same broken behavior for the `AUTHORIZER` env var since v13.x. Both mocking mechanisms (`sls-offline-authorizer-override` header and `AUTHORIZER` env var) appear to be broken when a `request`-type custom authorizer is defined, regardless of the `noAuth` configuration.