"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.

Written by the indexing model from the issue text.