fix(bindings): normalize perps order side

[cesarenaldi]

Summary

• normalize Perps order reads and order update events from upstream buy into SDK side: OrderSide
• add binding coverage for HTTP order reads and websocket order updates
• add a patch changeset for @polymarket/bindings and @polymarket/client

Verification

• pnpm test:bindings -- packages/bindings/src/perps/orders.test.ts
• pnpm lint
• pnpm typecheck

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Note

Medium Risk
This is a breaking shape change for any code reading buy on PerpsOrder or order updates; downstream client usage must switch to side.

Overview
Perps HTTP order reads (PerpsOrderSchema) and websocket order updates (PerpsOrderUpdateSchema) no longer expose upstream buy: boolean on parsed objects. Both schemas now map buy to side: OrderSide (BUY / SELL) during Zod transforms, aligning perps orders with the shared SDK order-side type.

Tests assert side for REST-shaped orders and compact WS update payloads. A patch changeset covers @polymarket/bindings and @polymarket/client.

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