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>

README.md

@@ -129,6 +129,22 @@ client, _ := attesto.NewClient(apiKey, attesto.WithHeadStore(attesto.NewFileHead
 client, _ = attesto.NewClient(apiKey, attesto.WithHeadStore(nil))
 ```
 
+## Iterating long listings
+
+Paginated `List*` methods have `Iter*` twins that walk limit/offset pages
+transparently; `Next` returns `(nil, nil)` when the listing is exhausted:
+
+```go
+it := client.IterTenantStreamEvents("str_...", 200)
+for {
+	event, err := it.Next(ctx)
+	if err != nil || event == nil {
+		break
+	}
+	process(event)
+}
+```
+
 ## Verify anchors on-chain
 
 `VerifyAnchorOnchain` checks an anchor epoch against the chain itself — one raw