feat(job-registry): add the job engine

src/infrastructure/scheduler/mod.rs

@@ -0,0 +1,33 @@
+//! Periodic job scheduler (Part 1 of the job-registry plan).
+//!
+//! In-memory registration + one-supervisor-task dispatch. Fires
+//! registered [`JobHandler`] implementations at their configured
+//! intervals with panic containment, timeout enforcement, and
+//! same-name exclusivity.
+//!
+//! # For future implementors
+//!
+//! - **You write a `JobHandler`.** Implement [`JobHandler::name`] +
+//!   [`JobHandler::run`] on your service. Nothing else. See
+//!   [`handler`] for the guidance doc-comment.
+//! - **DI wires the registration.** In `common/di.rs` (or wherever the
+//!   composition root lives), build an `Arc<JobRegistry>` once, register
+//!   every service that opts in, then call [`SchedulerEngine::start`].
+//! - **Should this loop actually be a scheduler job?** See the migration
+//!   criterion in `docs/plan/job-registry.md` — the primary question
+//!   is "would an operator plausibly trigger this manually?". Continuous
+//!   drains and event-reactive workers stay as their own loops.
+//!
+//! Part 2 (recoverable-run engine, DB-backed cursor + resume) is
+//! designed but not yet implemented. When it lands it will slot in
+//! as a sibling module without changing anything here.
+
+mod engine;
+mod handler;
+mod registry;
+mod types;
+
+pub use engine::SchedulerEngine;
+pub use handler::JobHandler;
+pub use registry::{JobEntry, JobRegistry, RegisterError};
+pub use types::{ErrCause, JobOutcome};