feat: add real-time TTY progress output for AWS env status polling

[ianaya89]

Summary

• Write provisioning progress directly to /dev/tty during spec revision polling, showing elapsed time and current vs target revision
• Gracefully skips output when no TTY is available (e.g. CI/CD environments)
• Provides real-time feedback during long-running terraform apply operations without polluting Terraform's stdout/stderr

Example output

  [altinitycloud] Waiting for "my-aws-env" to reach spec revision 5...
  [altinitycloud] [10s] my-aws-env: revision 3/5, connecting...
  [altinitycloud] [20s] my-aws-env: revision 3/5, connecting...
  [altinitycloud] [30s] my-aws-env: revision 3/5, waiting...
  [altinitycloud] [40s] my-aws-env: revision 4/5, waiting...
  [altinitycloud] [50s] my-aws-env: revision 5/5, ready!

Downsides

1. /dev/tty is Unix-only. On Windows openTTY returns nil gracefully (no breakage, but no output).
2. If a panic occurs between open and return, the file descriptor leaks (the defer Close() won't run). Minor edge case.
3. With a 30s poll interval and 60min timeout, output could reach ~120 lines in the worst case.