`Unrecognized named-value: 'matrix'` / `Available expression contexts: github, inputs, vars, needs, strategy, matrix, secrets, steps, job, runner, env`

Type: Bug

Create a `.github/workflows/ci.yml` file with:
```yaml
name: CI
on:
push:
workflow_dispatch:

env:
REGISTRY: ghcr.io
IMAGE_NAME: ${{ github.repository }}

jobs:
build-arch:
name: Build
permissions:
contents: read
packages: write
attestations: write
id-token: write

strategy:
fail-fast: false
matrix:
include:
- os: ubuntu-24.04
name: amd
- os: ubuntu-24.04-arm
name: arm

runs-on: ${{ matrix.os }}
outputs:
attestation-url: ${{ steps.attestation.outputs.attestation-url }}
${{ matrix.name }}-attestation-url: ${{ steps.attestation.outputs.attestation-url }}
my-matrix: ${{ matrix }}
${{ toJSON(matrix) }}: 'x'

steps:
- name: Checkout
uses: actions/checkout@v4

- name: Log in to the Container registry
uses: docker/login-action@v3
with:
registry: ${{ env.REGISTRY }}
username: ${{ github.actor }}
password: ${{ secrets.GITHUB_TOKEN }}

- name: Extract metadata (tags, labels) for Docker
id: meta
uses: docker/metadata-action@v5
with:
images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}

- name: Build and push Docker image
id: push
uses: docker/build-push-action@v6
with:
context: .
push: true
tags: ${{ steps.meta.outputs.tags }}
labels: ${{ steps.meta.outputs.labels }}

- name: Generate artifact attestation
id: attestation
uses: actions/attest-build-provenance@v2
with:
subject-name: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME}}
subject-digest: ${{ steps.push.outputs.digest }}
push-to-registry: true

combine-images:
name: Combine images
permissions:
contents: read
packages: write
attestations: write
id-token: write

runs-on: ubuntu-latest
steps:
- name: Checkout
uses: actions/checkout@v4

- name: Log in to the Container registry
uses: docker/login-action@v3
with:
registry: ${{ env.REGISTRY }}
username: ${{ github.actor }}
password: ${{ secrets.GITHUB_TOKEN }}
```

See a red-squiggly near `${{ matrix.name }}-attestation-url: ${{ steps.attestation.outputs.attestation-url }}`

Hover over `${{ matrix.name }}`

See:
```yaml
Unrecognized named-value: 'matrix'
Available expression contexts: github, inputs, vars, needs, strategy, matrix, secrets, steps, job, runner, env
```

View problem shows:
```yaml
Unrecognized named-value: 'matrix'
```

---

* If an expression is available, then it should be usable.
* If it isn't available, then it shouldn't be listed as available.

Extension version: 0.27.1
VS Code version: Code 1.98.0 (Universal) (6609ac3d66f4eade5cf376d1cb76f13985724bcb, 2025-03-04T21:06:18.612Z)
OS version: Darwin arm64 24.3.0
Modes:

System Info

|Item|Value|
|---|---|
|CPUs|Apple M1 Max (10 x 2400)|
|GPU Status|2d_canvas: enabled
canvas_oop_rasterization: enabled_on
direct_rendering_display_compositor: disabled_off_ok
gpu_compositing: enabled
multiple_raster_threads: enabled_on
opengl: enabled_on
rasterization: enabled
raw_draw: disabled_off_ok
skia_graphite: disabled_off
video_decode: enabled
video_encode: enabled
webgl: enabled
webgl2: enabled
webgpu: enabled
webnn: disabled_off|
|Load (avg)|7, 9, 10|
|Memory (System)|64.00GB (0.87GB free)|
|Process Argv|--crash-reporter-id 1fc67ee2-0174-4598-9f98-4537df0dd32c|
|Screen Reader|no|
|VM|0%|

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```