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

cmd/corestack-goose/main.go

@@ -0,0 +1,40 @@
+// Command corestack-goose authors provider-local SQL and Go migrations offline.
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	urfavecli "github.com/urfave/cli/v3"
+	"go.auvem.com/corestack/cmd/corestack-goose/internal/authoring"
+)
+
+func main() {
+	if err := command().Run(context.Background(), os.Args); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
+
+func command() *urfavecli.Command {
+	root := &urfavecli.Command{Name: "corestack-goose", Usage: "Author migrations before deployment"}
+	for _, name := range []string{"create", "fix"} {
+		root.Commands = append(root.Commands, &urfavecli.Command{Name: name,
+			Flags: []urfavecli.Flag{&urfavecli.StringFlag{Name: "dir", Value: ".", Usage: "Migration directory (defaults to the current working directory)"}},
+			Action: func(_ context.Context, cmd *urfavecli.Command) error {
+				if name == "create" {
+					if cmd.NArg() != 2 {
+						return fmt.Errorf("usage: create [--dir <dir>] <name> sql|go")
+					}
+					return authoring.Create(cmd.String("dir"), cmd.Args().Get(0), cmd.Args().Get(1))
+				}
+				if cmd.NArg() != 0 {
+					return fmt.Errorf("usage: fix [--dir <dir>]")
+				}
+				return authoring.Fix(cmd.String("dir"))
+			},
+		})
+	}
+	return root
+}