sdk(P1.7): auto-pagination iterators for every paginated list method

Each limit/offset list method gains an iterator twin that walks pages
transparently and stops on the first short page — same endpoints, no new API
surface: Python generators (iter_tenant_streams / _stream_events / _windows /
_checkpoints / iter_fork_evidence / iter_tenant_ivc_epochs), TypeScript async
iterators (for await ... of client.iterTenantStreamEvents(...)), and a Go
Iterator with Next(ctx) returning (nil, nil) at exhaustion, plus Iter* twins
on the client. Tests drain a 3-page mocked response set in order and confirm
a short first page ends iteration after exactly one request. READMEs updated.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

iterator_test.go

@@ -0,0 +1,65 @@
+package attesto
+
+import (
+	"context"
+	"testing"
+)
+
+func TestIteratorDrainsThreePagesInOrder(t *testing.T) {
+	pages := map[int][]M{
+		0: {{"seqNo": 1}, {"seqNo": 2}, {"seqNo": 3}},
+		3: {{"seqNo": 4}, {"seqNo": 5}, {"seqNo": 6}},
+		6: {{"seqNo": 7}},
+	}
+	calls := 0
+	it := NewIterator(func(_ context.Context, limit, offset int) ([]M, error) {
+		calls++
+		if limit != 3 {
+			t.Fatalf("limit = %d, want 3", limit)
+		}
+		return pages[offset], nil
+	}, 3)
+
+	var seqs []int
+	for {
+		item, err := it.Next(context.Background())
+		if err != nil {
+			t.Fatal(err)
+		}
+		if item == nil {
+			break
+		}
+		seqs = append(seqs, item["seqNo"].(int))
+	}
+	want := []int{1, 2, 3, 4, 5, 6, 7}
+	if len(seqs) != len(want) {
+		t.Fatalf("seqs = %v", seqs)
+	}
+	for i, v := range want {
+		if seqs[i] != v {
+			t.Fatalf("seqs = %v, want %v", seqs, want)
+		}
+	}
+	if calls != 3 {
+		t.Errorf("calls = %d, want 3", calls)
+	}
+}
+
+func TestIteratorStopsCleanlyOnShortFirstPage(t *testing.T) {
+	calls := 0
+	it := NewIterator(func(_ context.Context, _, _ int) ([]M, error) {
+		calls++
+		return []M{{"streamId": "str_only"}}, nil
+	}, 100)
+	first, err := it.Next(context.Background())
+	if err != nil || first == nil {
+		t.Fatalf("first = %v err = %v", first, err)
+	}
+	second, err := it.Next(context.Background())
+	if err != nil || second != nil {
+		t.Fatalf("second = %v err = %v", second, err)
+	}
+	if calls != 1 {
+		t.Errorf("calls = %d, want 1 (short page must end iteration)", calls)
+	}
+}