fix: Cap market order taker amount at 4 decimals to match API limit (#87)

[lushan888]

Fix for #87 — Market orders rejected due to taker amount precision

Problem

getMarketOrderRawAmounts rounds the taker amount using ROUNDING_CONFIG.amount (5-6 decimals for 0.001/0.0001 tick markets), but the CLOB API accepts at most 4 decimals for the taker amount. Result: orders are rejected server-side.

Fix

After the existing tick-size rounding logic, cap rawTakerAmt at 4 decimals using roundDown for both BUY and SELL branches. This is a 4-line change with a named constant.

Verification

Scenario	Before	After
BUY $5 at 0.998 (0.001-tick)	takerAmount = 5010020 (5 decimals)	takerAmount = 5010000 (4 decimals) ✓
SELL 7.77 shares at 0.998 (0.001-tick)	takerAmount = 7754460 (5 decimals)	takerAmount = 7754000 (4 decimals) ✓

Impact

• Minimal: existing rounding logic is preserved, only capped to 4 decimals when it exceeds
• No API changes — same function signature, same types

Wallet (Base): 0xaa9e4971e0973065513b18dEF9eC06Eb1F39D7A2

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Note

Low Risk
Localized rounding change in market order amount calculation with no API or signature changes; slight downward bias on taker size only when capping applies.

Overview
Fixes CLOB rejections when market orders compute a taker amount with more than four decimal places (common on 0.001/0.0001 tick markets where roundConfig.amount allows 5–6 decimals).

getMarketOrderRawAmounts now defines MAX_TAKER_DECIMALS = 4 and, after the existing tick-size rounding on both BUY and SELL, applies roundDown on rawTakerAmt when precision exceeds that cap. Maker-side rounding and the function signature are unchanged; only the final taker value sent through buildMarketOrderCreationArgs is adjusted to match the API limit.

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