feat(lifecycle): supervise modules and managed workers

README.md

@@ -1,6 +1,6 @@
 # corestack go
 
-Shared Go building blocks. The first one is `docs`, a checker for architecture decision records (ADRs) and implementation plans.
+Shared Go building blocks. Includes `docs`, a checker for architecture decision records (ADRs) and implementation plans, and `lifecycle`, a service and worker coordinator.
 
 ## docs
 
@@ -20,6 +20,26 @@ docs check [--root DIR]                                # prints path:line: messa
 
 The format is specified in [docs/docs-format.md](docs/docs-format.md); that document is the complete rule set. Exit status is `0` when every record is valid, `1` when problems are reported and `2` for usage errors.
 
+## lifecycle
+
+`go.auvem.com/corestack/lifecycle` sets up modules in registration order, runs
+services concurrently, and tears down successful setups in reverse order.
+Construct an `App` with a required `*slog.Logger`, register `Module` callbacks,
+and call `Run(ctx)` once. See the [two-service example](lifecycle/example_test.go).
+
+Launch background work with `app.Go(ctx, name, fn)` using the callback's lifecycle
+context or a descendant, and handle admission errors. Run waits for every service
+and admitted worker; raw goroutines remain your responsibility. First failure or
+an injected signal cancels work before teardown. One shared shutdown deadline
+(default 30 seconds) covers hooks and callback completion; a second signal
+abandons shutdown. Callbacks must cooperate: abandonment cannot kill goroutines,
+and the caller owns process exit and any unreleased resources.
+
+The caller owns signal subscription, SIGINT/SIGTERM filtering, a channel buffered
+for at least two signals, and subscription cleanup. Nil signals disable reception.
+There are no signal subscriptions, process exits, external dependencies or CLI
+integration in this package.
+
 ## Status
 
 No support is guaranteed. Breaking changes, including to the format rules, may happen before 1.0 and are listed in the release notes.