ci: match fixture paths in Super-Linter

Match absolute fixture paths passed by Super-Linter and satisfy repository analysis for the coverage test helper.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: MariusStorhaug

.github/linters/.yaml-lint.yml

@@ -3,4 +3,4 @@ extends: relaxed
 
 # Official conformance fixtures intentionally preserve invalid and unusual YAML.
 ignore: |
-  tests/fixtures/
+  **/tests/fixtures/**

tests/TestBootstrap.ps1

@@ -13,6 +13,10 @@ if ($null -eq $yamlModule) {
 }
 
 function Get-TestYamlFingerprintLength {
+    <#
+        .SYNOPSIS
+        Returns structural fingerprint lengths for a YAML alias graph.
+    #>
     param (
         [Parameter(Mandatory)]
         [string] $Yaml