Add services pcport command

[elliotthilaire-ca]

Closes #2783

Summary

This command returns the port that process-compose is running on. That makes it more feasible to use the process-compose api in scripting.

For example:

pcport=$(devbox services pcport)
curl http://localhost:$pcport/process/good-server | jq ".status, .is_ready"

How was it tested?

With process-compose running:

$ dist/devbox services pcport
53173

$ echo $?
0

With process-compose stopped:

$ dist/devbox services pcport

Error: process-compose is not running or it's config is missing. To start it, run `devbox services up`
source: failed to find projectDir /Users/elliott.hilaire/github.com/elliotthilaire-ca/devbox in config.Instances

$ echo $?
1

Community Contribution License

All community contributions in this pull request are licensed to the project
maintainers under the terms of the
Apache 2 License.

By creating this pull request, I represent that I have the right to license the
contributions to the project maintainers under the Apache 2 License as stated in
the
Community Contribution License.

AI disclosure

Claude code assisted in creating this PR.

[elliotthilaire-ca]

This PR potentially closes #2453 as once the process-compose port is fetched the status of individial processes can be checked using the api.