feat(migrate): add lifecycle commands and standalone authoring (#18)

Add apply/require startup policies and five database-only migration commands.

Provide standalone corestack-goose creation and reconciliation with fresh
provider-local Go registrations. Default optional --dir to the working directory.
Document the production boundary and source recovery requirements.

Closes #9

migrate/migrate.go

@@ -23,10 +23,13 @@ import (
 // across providers/processes. PostgreSQL connections must preserve session
 // affinity (transaction-pooling proxies cannot safely hold session locks).
 //
-// Use the returned Provider's Up, UpTo, DownTo, Status, GetDBVersion, GetVersions,
-// and HasPending methods directly. Create migration files with Goose's create
-// command; lexical filename order must match numeric version order. Go migrations
-// are registered per provider; global Go registration is ignored.
+// Use the returned Provider's Up, UpTo, Down, DownTo, Status, GetDBVersion, GetVersions,
+// and HasPending methods directly. Create and reconcile sources with the standalone
+// corestack-goose tool (go run go.auvem.com/corestack/cmd/corestack-goose).
+// Pass migrations.GoMigrations()... from its generated package; stock Goose Go
+// output uses an incompatible global init registry. Lexical filename order must
+// match numeric version order. Each provider needs fresh Go registrations;
+// global Go registration is ignored.
 func New(db *sql.DB, dialect goose.Dialect, files embed.FS, dir string, logger *slog.Logger, migrations ...*goose.Migration) (*goose.Provider, error) {
 	for i, migration := range migrations {
 		if migration == nil {