perf: prewarm order metadata and reuse order hash

[casterkay]

Summary

• add a public warm_up_order_metadata API so callers can populate order-construction metadata before latency-sensitive order creation
• expose the EIP-712 hash already produced while signing on SignedOrderV1 and SignedOrderV2
• preserve V1, V2 EOA/proxy/safe, and POLY_1271 signatures and keep order_hash out of submitted JSON

Why

Order creation may otherwise perform tick-size, negative-risk, fee, version, and builder-fee REST lookups on first use. Consumers that need the venue order ID also currently rebuild and hash the same typed data after signing. This gives callers public, dependency-owned APIs for both optimizations without copying private internals.

Tests

• python -m pytest -q — 232 passed, 15 subtests passed
• regressions prove warmed V1/V2 first orders issue zero metadata GETs
• regressions prove each signature path encodes/hashes typed order data once and retains exact signature/hash compatibility
• regressions prove order_hash is excluded from the order wire payload

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Note

Low Risk
Performance and API surface additions on order construction; signing semantics and wire payloads are preserved with regression tests.

Overview
Adds warm_up_order_metadata(condition_id, builder_code?) so callers can prefetch CLOB market info (tick size, neg risk, fee metadata), V1 per-token fee caps, and optional builder fee rates before latency-sensitive create_order / create_market_order calls. Builder fee loading is centralized in __load_builder_fee_rate, reused by warmup and the existing lazy cache path.

Signed orders now carry an order_hash field on SignedOrderV1 and SignedOrderV2, populated from the same EIP-712 encode/sign step via _build_order_signature_and_hash (one encode_typed_data per build for EOA-style paths; POLY_1271 still hashes once for the hash). order_to_json_v1 / order_to_json_v2 do not send order_hash on the wire.

Tests cover warmup avoiding metadata GETs on first orders, stable signature/hash values, single-encode behavior, and JSON exclusion of order_hash.

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