fix: Remove invalid pattern properties from showtime workflows

- Remove unsupported `pattern` property from workflow_dispatch inputs
- Add one-time push trigger to showtime-cleanup.yml for workflow registration
- Runtime validation still handled in bash steps

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

.github/workflows/showtime-trigger.yml

@@ -16,7 +16,6 @@ on:
         description: 'Specific SHA to deploy (optional, defaults to latest)'
         required: false
         type: string
-        pattern: '^[a-f0-9]{40}$'
 
 # Common environment variables for all jobs
 env: