fix(templates): use env lookup for Telegram demo verification

[tbrandenburg]

Motivation

• The template's verification step relied on a helper (get_workflow_var) that may not be available in generated scripts, causing runtime errors like get_workflow_var: command not found.
• CI runs with placeholder or missing Telegram credentials produced false failures because successful dry-runs were not recognized.
• The Telegram delivery node needed to be non-fatal so verification logic can decide final workflow success.

Description

• Replaced get_workflow_var usage with a direct environment lookup using telegram_success="${TELEGRAM_SUCCESS:-false}" in templates/enhanced/ai-to-telegram-template.yaml.
• Added demo-mode detection that sets telegram_demo_mode to true when credentials are missing or match known placeholder values, and made the Telegram node error_handling: 'continue' to avoid aborting the workflow on delivery failure.
• Emit a clear success marker ("Workflow completed successfully") and exit 0 when delivery succeeds or when running in demo mode, and improved message length counting with printf '%s' to avoid word-splitting.

Testing

• Ran the full QA pipeline with MAKEFLAGS= make qa which completed successfully and reported "All QA checks passed!".
• The test run included linting, formatting, tsc build, and the full vitest suite which passed (all tests green).

---

Codex Task