Fix release install validation for starter workflows

[bigboateng]

Summary

• verify new starters stop until they are implemented
• replace each starter with a minimal completed workflow during the install journey
• validate workflow health separately from generated agent adapters

Test plan

• ran the full TypeScript, Python, Go, and Rust install journey locally against v0.1.20
• PR workflow validates the release script
• merge will publish v0.1.21 and run all six native install journeys