sdk(P1.2): payload commitment + safe-number preflight in all three SDKs

Adds payload_commitment / metadata_commitment / verify_payload_commitment
and assert_commitment_safe_numbers to the Python, TypeScript, and Go SDKs,
each building on the frozen canonical_json/domain_hash primitives (no change
to their byte output). The number preflight is a byte-for-byte port of the
backend assert_commitment_safe_numbers (floats rejected, |int| > 2^53-1
rejected, bool exempt) and is wired into the v2 log_event / log_events send
path, raising a typed AttestoUnsafeNumberError with the JSON path so the rule
fails at dev time rather than as a production 422; preflight=False /
SkipPreflight defers to the server.

New shared corpus golden-vectors/sdk-parity/canonical-numbers.json (15 accept
+ 8 reject), accept-hashes generated from the backend _commitment. Proven:
Python = TypeScript = Go = backend produce byte-identical commitment hashes
for every accept vector and identical reject paths (the Go float64-vs-Python-
int serialization parity holds). READMEs updated per SDK.

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

client.go

@@ -161,6 +161,16 @@ func (c *Client) LogEvent(ctx context.Context, streamID string, input EventInput
 	if err := normalizeEventInput(&input); err != nil {
 		return nil, err
 	}
+	// Reject commitment-unsafe numbers locally so the developer sees the rule at
+	// dev time rather than as a production 422; SkipPreflight defers to the server.
+	if !skipPreflight(options) {
+		if err := AssertCommitmentSafeNumbers(input.Payload, "$.payload"); err != nil {
+			return nil, err
+		}
+		if err := AssertCommitmentSafeNumbers(input.Metadata, "$.metadata"); err != nil {
+			return nil, err
+		}
+	}
 	var out EventReceipt
 	err := c.requestJSON(ctx, http.MethodPost, "/v2/streams/"+url.PathEscape(streamID)+"/events", nil, input, idempotency(options), &out)
 	return &out, err
@@ -170,10 +180,19 @@ func (c *Client) LogEvents(ctx context.Context, streamID string, events []EventI
 	if len(events) > 1000 {
 		return nil, errors.New("max 1000 events per batch")
 	}
+	preflight := !skipPreflight(options)
 	for i := range events {
 		if err := normalizeEventInput(&events[i]); err != nil {
 			return nil, fmt.Errorf("event %d: %w", i, err)
 		}
+		if preflight {
+			if err := AssertCommitmentSafeNumbers(events[i].Payload, fmt.Sprintf("$.events[%d].payload", i)); err != nil {
+				return nil, err
+			}
+			if err := AssertCommitmentSafeNumbers(events[i].Metadata, fmt.Sprintf("$.events[%d].metadata", i)); err != nil {
+				return nil, err
+			}
+		}
 	}
 	body := M{"events": events}
 	var out EventBatchResponse
@@ -558,6 +577,10 @@ func retryable(status int) bool {
 	}
 }
 
+func skipPreflight(options []RequestOptions) bool {
+	return len(options) > 0 && options[0].SkipPreflight
+}
+
 func idempotency(options []RequestOptions) string {
 	if len(options) > 0 && options[0].IdempotencyKey != "" {
 		return options[0].IdempotencyKey