fix(prompts): reduce margin usage from 95% to 88% for Hyperliquid liquidation buffer (#666)

## Problem
Users with small accounts (<$200) encounter Hyperliquid error:
"Insufficient margin to place order. asset=1"

Real case: $98.89 account failed to open position

## Root Cause
5% reserve insufficient for:
- Trading fees (~0.04%)
- Slippage (0.01-0.1%)
- Liquidation margin buffer (Hyperliquid requirement)

Additionally, undefined "Allocation %" parameter caused confusion.

## Solution
1. Reduce margin usage rate from 95% to 88% (reserve 12%)
2. Remove undefined "Allocation %" parameter
3. Add small account example ($98.89) for clarity

## Example ($98.89 account)
Before: $93.95 margin → $4.75 remaining ❌
After:  $87.02 margin → $11.87 remaining ✅

## Modified Files
- prompts/adaptive.txt
- prompts/default.txt
- prompts/nof1.txt

## Testing
Verified with $98.89 account on z-dev branch - successful order placement

Fixes #549

prompts/nof1.txt

@@ -55,15 +55,15 @@ You have exactly SIX possible actions per decision cycle:
 
 ## Calculation Steps:
 
-1. **Available Margin** = Available Cash × 0.95 × Allocation % (reserve 5% for fees)
+1. **Available Margin** = Available Cash × 0.88 (reserve 12% for fees, slippage & liquidation margin buffer)
 2. **Notional Value** = Available Margin × Leverage
 3. **position_size_usd** = Notional Value (this is the value for JSON)
 4. **Position Size (Coins)** = position_size_usd / Current Price
 
-**Example**: Available Cash = $500, Leverage = 5x, Allocation = 100%
-- Available Margin = $500 × 0.95 × 100% = $475
-- position_size_usd = $475 × 5 = **$2,375** ← Fill this value in JSON
-- Actual margin used = $475, remaining $25 for fees
+**Example**: Available Cash = $500, Leverage = 5x
+- Available Margin = $500 × 0.88 = $440
+- position_size_usd = $440 × 5 = **$2,200** ← Fill this value in JSON
+- Actual margin used = $440, remaining $60 for fees, slippage & liquidation protection
 
 ## Sizing Considerations