Make caff PID detection more robust

[codeforester]

Summary

• Replace pgrep ... | head -1 in caff with explicit pgrep status handling
• Distinguish missing target processes from real pgrep failures
• Parse existing caffeinate command arguments defensively instead of assuming a fixed argument position
• Recognize multiple valid caffeinate -w forms:
  • caffeinate -iw <pid>
  • caffeinate -i -w <pid>
  • caffeinate -w <pid> -i
• Add focused BATS coverage for alternate caffeinate argument shapes and pgrep failures
• Mark the TODO item complete

Testing

• bash -n cli/bash/commands/caff/caff.sh
• bats cli/bash/commands/caff/tests/caff.bats
• bats cli/bash/commands/basectl/tests/basectl.bats