MSYS curl on Windows has SSL/TLS failures and path mangling issues.
Replaced curl references in checkpoint and phase-prompt templates with
Node.js fetch() which works cross-platform.
Changes:
- checkpoints.md: server readiness check uses fetch() instead of curl
- checkpoints.md: added cross-platform note about curl vs fetch
- checkpoints.md: verify tags use fetch instead of curl
- phase-prompt.md: verify tags use fetch instead of curl
Partially addresses #899 (patch 1 of 6)
8520424a62