fix(workflow): escape PowerShell variable delimiter in ai-issue-triage (#294)

The colon after $issueNumber was being interpreted as a scope modifier
(like $global:var). Changed to ${issueNumber}: to properly delimit
the variable name.

Fixes ParserError: Variable reference is not valid. ':' was not followed
by a valid variable name character.

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Co-authored-by: rjmurillo[bot] <rjmurillo-bot@users.noreply.github.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: rjmurillo-bot

.github/workflows/ai-issue-triage.yml

@@ -566,7 +566,7 @@ jobs:
             if (-not $hasTriageMarker) {
               # Get issue title for logging
               $issueTitle = gh issue view $issueNumber --json title --jq '.title' 2>$null
-              Write-Host "  Issue #$issueNumber: $issueTitle - NOT TRIAGED" -ForegroundColor Yellow
+              Write-Host "  Issue #${issueNumber}: $issueTitle - NOT TRIAGED" -ForegroundColor Yellow
               $untriagedIssues += $issueNumber
             }
           }