Restructure: move src to core/ crate, move cmd/supervisor.rs to core/src/bin/supervisor.rs, create workspace

core/src/job.rs

@@ -0,0 +1,3 @@
+// Re-export job types from the hero-job crate
+pub use hero_job::{Job, JobBuilder, JobStatus, JobError};
+use hero_job_client::{Client, ClientBuilder};