Add optional agent-qc support to generated validation

[rogerchappel]

Summary

• make generated repos point their primary verification command at bash scripts/validate.sh
• expand the generated validation script to run standard local package scripts and optionally run agent-qc ready when available
• document the optional agent-qc hook and extend smoke coverage for both installed and missing agent-qc

Testing

• pnpm check
• pnpm build
• pnpm check:templates
• pnpm smoke:init