Restore puts submodules on a branch at their pin

A restored submodule whose pin is a branch tip ends on that branch instead
of a detached HEAD: the local branch tracking the ref, else the ref created
as a tracking branch, else another local branch, else another remote branch
at the pin. No branch is moved; in-sync submodules are included (D28).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/submodule/git/switch.go

@@ -107,7 +107,7 @@ func (p *Provider) Switch(ctx context.Context, path string, b submodule.Branch)
 			return "", err
 		}
 	}
-	if err := p.restoreRepo(ctx, dir, b.SHA); err != nil {
+	if err := p.restoreRepo(ctx, dir, b.SHA, nil); err != nil { // HEAD goes on b below
 		return "", err
 	}