"Unable to resolve action" for any action

Every action in an .yml file gives an error `Unable to resolve action "actions/checkout@v4", repository or version not found` - even fundamental stuff like `- uses: actions/checkout@v4`

**To Reproduce**
- Make a file like this one (autogenerated by github.com):
```
name: .NET
on:
push:
branches: [ "main" ]
jobs:
build:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v4
- name: Setup .NET
uses: actions/setup-dotnet@v4
with:
dotnet-version: 9.0.x
- name: Restore dependencies
run: dotnet restore
- name: Build
run: dotnet build --no-restore

```
- Open the Problems tab in VSCode.
- Lines 9 and 11 now give an error:
```
[{
"resource": "/[repo_path]/.github/workflows/dotnet.yml",
"owner": "_generated_diagnostic_collection_name_#7",
"severity": 8,
"message": "Unable to resolve action `actions/checkout@v4`, repository or version not found",
"startLineNumber": 9,
"startColumn": 13,
"endLineNumber": 9,
"endColumn": 32
}]
```

**Expected behavior**
Expected no false errors.

**Screenshots**

**Extension Version**
`v0.27.0`

**Additional context**
Add any other context about the problem here.

Reproduce the diagnostics in .github/workflows/dotnet.yml using actions/checkout@v4 and actions/setup-dotnet@v4, then trace the extension's action-resolution entry point. Confirm the fix by opening the Problems tab and verifying that valid actions no longer produce false repository or version errors.

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