feat(ci): use TTL labels for showtime cleanup (#36643)

Co-authored-by: Claude <noreply@anthropic.com>

.github/workflows/showtime-cleanup.yml

@@ -7,12 +7,6 @@ on:
 
   # Manual trigger for testing
   workflow_dispatch:
-    inputs:
-      max_age_hours:
-        description: 'Maximum age in hours before cleanup'
-        required: false
-        default: '48'
-        type: string
 
 # Common environment variables
 env:
@@ -38,13 +32,5 @@ jobs:
 
       - name: Cleanup expired environments
         run: |
-          MAX_AGE="${{ github.event.inputs.max_age_hours || '48' }}"
-
-          # Validate max_age is numeric
-          if [[ ! "$MAX_AGE" =~ ^[0-9]+$ ]]; then
-            echo "❌ Invalid max_age_hours format: $MAX_AGE (must be numeric)"
-            exit 1
-          fi
-
-          echo "Cleaning up environments older than ${MAX_AGE}h"
-          python -m showtime cleanup --older-than "${MAX_AGE}h"
+          echo "Cleaning up environments respecting TTL labels"
+          python -m showtime cleanup --respect-ttl