tabSize setting is inconsitently applied

Describe the bug

I have tabSize set to 4:

"[yaml]": {
	"editor.insertSpaces": true,
	"editor.tabSize": 4,
	"editor.autoIndent": "keep",
	"diffEditor.ignoreTrimWhitespace": false,
	"editor.quickSuggestions": {
		"other": true,
		"comments": false,
		"strings": true
	}
}

vscode-yaml inconsistently applies the tab size, resulting in mixed indents of 4 and 6.

Here's an example of some yaml from a Github Action I'm working on that the extension should not be reformatting:

# ...
runs:
    using: "composite"
    steps:
    -   name: Setup environment variables
        id: env_vars
        run: |
            export AWS_REGION=us-west-2 >> $GITHUB_ENV
# ...

You can see in this screenshot that tab size is consistently 4 spaces:

Expected Behavior

When formatting happens, the above should be left untouched

Current Behavior

vscode-yaml removes the spaces after the hyphen and adds an unnecessary indent, reformatting to the following:

runs:
    using: "composite"
    steps:
        - name: Setup environment variables
          id: env_vars
          run: |
              export AWS_REGION=us-west-2 >> $GITHUB_ENV

This uses tab size 4 sometimes, other times tab size 2. The problem is removing the spaces after the hyphen... - name: should not be changed to - name:!

You can see in this screenshot that this is inconsistent tab size; id and run are half indented:

This isn't a problem with tab size 2, since - name: is implicitly tab size 2.

Steps to Reproduce

1. set tabSize to 4
2. run formatting

Environment

• Windows
• Mac
• Linux
• other (please specify)

Start by reproducing the formatter behavior in vscode-yaml with tabSize set to 4 and the provided GitHub Actions YAML. Compare the formatted output with the expected unchanged indentation, including the spaces after -; done means formatting preserves the four-space layout and - name: spacing.