fix(sdk-python): harden cryptographic order salts, preserve zero salts, and enforce cancellation preflight validation

[magqqgq]

Description

This PR hardens the Python SDK against predictable order identifiers, implicit truthiness bugs on order parameters, and unvalidated cancellation requests[cite: 35, 36, 37]. It replaces weak pseudo-random generators with cryptographic selections, protects explicit zero-salt assignments, and enforces preflight token validation prior to order cancellation submission[cite: 35, 36, 37].

Key Changes

• Cryptographic Order Salts (predict_sdk/_internal/utils.py):
  • Replaced the non-cryptographic random.randint with Python's standard secrets.randbelow(MAX_SALT + 1) to ensure secure, unbiased order salt generation[cite: 35].
• Zero-Salt Preservation (predict_sdk/order_builder.py):
  • Replaced truthiness checks (data.salt) with an explicit None check (data.salt is not None). This ensures that an explicitly provided salt=0 is correctly preserved and serialized as "0" instead of being overwritten by a random value[cite: 36].
• Cancellation Preflight Validation (predict_sdk/order_builder.py):
  • Enforced the existing options.with_validation contract by calling validate_token_ids_async before encoding and dispatching cancelOrders, preventing late on-chain failures due to incorrect market configurations[cite: 36].
• Regression Coverage (tests/test_order_builder.py):
  • Added unit test coverage verifying zero-salt preservation and the correct rejection behavior when invalid token IDs are passed during cancellations[cite: 37].

Validation & Testing

• Syntax & Compiling: Python source files pass syntax compilation cleanly (python -m py_compile).

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Note

Medium Risk
Touches order identity (salts), order serialization, and on-chain cancel behavior; changes are narrow but affect trading and signing paths.

Overview
Hardens order-building and cancellation in the Python SDK with three targeted fixes.

Order salts now use secrets.randbelow instead of random.randint, so generated salts are cryptographically unpredictable within [0, MAX_SALT].

Explicit salt=0 is preserved in build_order by checking data.salt is not None instead of truthiness, so "0" is no longer replaced by a random salt.

Cancellation honors CancelOrdersOptions.with_validation (default True): when enabled, cancel_orders_async runs validate_token_ids_async first and raises InvalidNegRiskConfig instead of sending a doomed cancelOrders transaction.

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