Workflow dispatch fails for workflows in git submodules

**Describe the bug**
When attempting to trigger a GitHub Actions workflow located in a git submodule (e.g., `host/.github/workflows/deploy.yml`), the extension fails with a 404 "Not Found" error. The extension incorrectly attempts to dispatch the workflow to the parent repository instead of the submodule's separate GitHub repository.

**To Reproduce**
Steps to reproduce the behavior:
1. Have a git repository with a submodule that has its own separate GitHub repository
2. The submodule contains GitHub Actions workflows in `.github/workflows/`
3. Open the workflow file in VSCode
4. Right-click and select "Trigger Run" or use the GitHub Actions explorer
5. See error: `404 Not Found` or similar repository not found error

**Expected behavior**
The extension should:
1. Detect that the workflow is located in a git submodule
2. Identify the correct GitHub repository for that submodule
3. Dispatch the workflow to the correct repository, not the parent

**Screenshots**
The error appears in the VSCode debug console when attempting to dispatch a workflow in the web submodule:

The extension is attempting to dispatch to the parent repository instead of the submodule's separate GitHub repository.

A user-facing error notification is displayed:

**Note:** Request IDs and repository names in the screenshot have been redacted for privacy.

**Extension Version**
`v0.31.5`

**Additional context**
This occurs in monorepo setups where submodules are separate GitHub repositories with their own workflows.
```
monorepo/ (Parent repo: github.com/owner/monorepo)
└── submodule/ (Submodule: github.com/owner/submodule)
└── .github/workflows/
└── deploy.yml ← Should dispatch to submodule repo
```

The extension's workflow dispatch logic needs to be aware of git submodules and route dispatch requests to the appropriate repository.

Reproduce the failure with a parent repository containing a submodule workflow at .github/workflows/deploy.yml, using Trigger Run or the GitHub Actions explorer. Trace the workflow-dispatch path and how the opened file's repository is identified. Done means dispatching targets the submodule repository and the 404 no longer occurs.

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