sdk(P1.3): inclusion, checkpoint-chain, and completeness verification

Completes the offline verification stack (P1.2 -> P1.1 -> P1.3) in all three
SDKs, each a faithful port of the backend windows.py / checkpoints.py math on
top of the frozen canonical/domain-hash primitives:

- verify_inclusion_proof: fold a window inclusion proof to the window root
  (domain attesto.v2.window; left sibling -> node(sibling,current), right ->
  node(current,sibling)).
- verify_checkpoint_root: recompute a checkpoint root from window hashes
  (domain attesto.v2.checkpoint), with an odd node at any level **promoted
  unchanged** rather than duplicated/hashed with itself (the place a naive
  Merkle port silently diverges).
- verify_checkpoint_extension: current.from_seq_no == previous.to_seq_no + 1
  and current.previous_checkpoint_hash == previous.checkpoint_hash.
- verify_completeness: proves no events were omitted in a range -- gap-free
  seq_no coverage plus prev_event_hash chaining to the previous event_hash.

New corpus golden-vectors/sdk-parity/inclusion.json (5-leaf window exercising
the promoted odd node, 3-window checkpoint root, extension + completeness
negatives), exported from the backend functions. Proven: Python = TypeScript =
Go = backend agree on every case. READMEs updated per SDK.

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

proofstream_parity_test.go

@@ -109,6 +109,77 @@ func TestParityReceiptVerification(t *testing.T) {
 	}
 }
 
+type inclusionParityVectors struct {
+	Inclusion []struct {
+		ID       string          `json:"id"`
+		LeafHash string          `json:"leaf_hash"`
+		Proof    []InclusionStep `json:"proof"`
+		RootHash string          `json:"root_hash"`
+		ExpectOK bool            `json:"expect_ok"`
+	} `json:"inclusion"`
+	CheckpointRoot []struct {
+		ID           string   `json:"id"`
+		WindowHashes []string `json:"window_hashes"`
+		ExpectedRoot string   `json:"expected_root"`
+		ExpectOK     bool     `json:"expect_ok"`
+	} `json:"checkpoint_root"`
+	CheckpointExtension []struct {
+		ID       string         `json:"id"`
+		Previous map[string]any `json:"previous"`
+		Current  map[string]any `json:"current"`
+		ExpectOK bool           `json:"expect_ok"`
+	} `json:"checkpoint_extension"`
+	Completeness []struct {
+		ID        string           `json:"id"`
+		Events    []map[string]any `json:"events"`
+		FromSeqNo int              `json:"from_seq_no"`
+		ToSeqNo   int              `json:"to_seq_no"`
+		ExpectOK  bool             `json:"expect_ok"`
+	} `json:"completeness"`
+}
+
+func TestParityInclusionAndCheckpoint(t *testing.T) {
+	path := filepath.Join("..", "..", "golden-vectors", "sdk-parity", "inclusion.json")
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("read inclusion vectors: %v", err)
+	}
+	var v inclusionParityVectors
+	if err := json.Unmarshal(raw, &v); err != nil {
+		t.Fatalf("decode inclusion vectors: %v", err)
+	}
+	for _, c := range v.Inclusion {
+		ok, err := VerifyInclusionProof(c.LeafHash, c.Proof, c.RootHash)
+		if err != nil {
+			t.Fatalf("%s: %v", c.ID, err)
+		}
+		if ok != c.ExpectOK {
+			t.Errorf("inclusion %s: ok=%v want %v", c.ID, ok, c.ExpectOK)
+		}
+	}
+	for _, c := range v.CheckpointRoot {
+		ok, err := VerifyCheckpointRoot(c.WindowHashes, c.ExpectedRoot)
+		if err != nil {
+			t.Fatalf("%s: %v", c.ID, err)
+		}
+		if ok != c.ExpectOK {
+			t.Errorf("checkpoint_root %s: ok=%v want %v", c.ID, ok, c.ExpectOK)
+		}
+	}
+	for _, c := range v.CheckpointExtension {
+		report := VerifyCheckpointExtension(c.Previous, c.Current)
+		if report.OK != c.ExpectOK {
+			t.Errorf("extension %s: ok=%v want %v (%v)", c.ID, report.OK, c.ExpectOK, report.Problems)
+		}
+	}
+	for _, c := range v.Completeness {
+		report := VerifyCompleteness(c.Events, c.FromSeqNo, c.ToSeqNo)
+		if report.OK != c.ExpectOK {
+			t.Errorf("completeness %s: ok=%v want %v (%v)", c.ID, report.OK, c.ExpectOK, report.Problems)
+		}
+	}
+}
+
 func TestParityVerifyPayloadCommitment(t *testing.T) {
 	for _, c := range loadParityVectors(t).Accept {
 		commitment, err := PayloadCommitment(c.Payload)