feat(18.1-08): detached admin bulk actions run outside the framework transaction

- pact.AdminBulkAction.Detached (json:"-"): opt-in; records loaded through the list scope without row locks, no write transaction in the context
- cabana BulkAction: detached branch with the same empty, partial-selection, failure and message rules; lockScoped is loadScoped with lock, the locked path unchanged
- docs: admin-controllers bulk route list, pact and cabana READMEs

modules/pact/capabilities.go

@@ -281,18 +281,29 @@ type HasAdminActions interface {
 // keys or literal text: Label is the menu item, Confirm the confirmation
 // question, and an empty Confirm means the framework's default confirm text.
 // Permissions are checked in addition to the controller's
-// RequiredPermissions.
+// RequiredPermissions. Detached opts an action out of the framework
+// transaction (see the field).
 type AdminBulkAction struct {
 	Name        string
 	Label       string
 	Confirm     string
 	Permissions []string
 	Run         func(ctx context.Context, in AdminBulkActionInput) (AdminBulkActionResult, error) `json:"-"`
+	// Detached runs Run outside the framework transaction. The selected
+	// records are loaded through the same ListExtendQuery scope, with the
+	// same empty and partial-selection rules, but without row locks, and
+	// the context carries no write transaction (cabana.TxFromContext
+	// reports none); Run opens the short transactions it needs. An action
+	// that calls an external service sets it, so that no transaction or row
+	// lock is held across the call. What such an action saved before a
+	// later failure stays saved.
+	Detached bool `json:"-"`
 }
 
 // AdminBulkActionInput is what the framework hands an AdminBulkAction.
 // Records are pointers to the controller's model, loaded and row-locked
-// through the controller's ListExtendQuery scope and ordered by primary key.
+// through the controller's ListExtendQuery scope and ordered by primary key
+// (loaded without row locks for a Detached action).
 // A bulk action never receives ids, so an id list can never become an
 // unscoped lookup.
 type AdminBulkActionInput struct {