Fix update-mslearn-dates action sed delimiter and test assertions

- Change sed delimiter from / to | so date slashes (MM/DD/YYYY) don't break the substitution
- Update test regex to accept both / and | sed delimiters
- Update test regex to accept optional -u flag on git add

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: flanakin

.github/workflows/update-mslearn-dates.yml

@@ -43,7 +43,7 @@ jobs:
             # Check if file has ms.date in frontmatter and update it
             if grep -q "^ms\.date:" "$file"; then
               # Use sed to replace the ms.date line
-              sed -i "s/^ms\.date:.*$/ms.date: $CURRENT_DATE/" "$file"
+              sed -i "s|^ms\.date:.*$|ms.date: $CURRENT_DATE|" "$file"
               echo "  Updated ms.date in $file"
             else
               echo "  No ms.date found in $file, skipping"

src/powershell/Tests/Unit/Action.UpdateMsLearnDates.Tests.ps1

@@ -80,7 +80,7 @@ Describe 'update-mslearn-dates GitHub Action' {
 
         It 'Should use sed to replace ms.date line' {
             $workflowContent | Should -Match 'sed -i'
-            $workflowContent | Should -Match 's/\^ms\\\.date:'
+            $workflowContent | Should -Match 's[/|]\^ms\\\.date:'
         }
 
         It 'Should have step to check for changes before committing' {
@@ -109,7 +109,7 @@ Describe 'update-mslearn-dates GitHub Action' {
     Context 'Sed command validation' {
         It 'Should have correct sed regex to match ms.date at line start' {
             # The sed command should use ^ to anchor to start of line
-            $workflowContent | Should -Match 's/\^ms\\\.date:\.\*\$/ms\.date:'
+            $workflowContent | Should -Match 's[/|]\^ms\\\.date:\.\*\$[/|]ms\.date:'
         }
 
         It 'Should replace entire ms.date line' {
@@ -124,7 +124,7 @@ Describe 'update-mslearn-dates GitHub Action' {
         }
 
         It 'Should only add docs-mslearn files to commit' {
-            $workflowContent | Should -Match 'git add docs-mslearn/'
+            $workflowContent | Should -Match 'git add (-u )?docs-mslearn/'
         }
     }
 }