feat(grid): auto-adjust grid direction based on box breakouts

Add GridDirection type with 5 states:
- neutral (50% buy + 50% sell)
- long/short (100% one direction)
- long_bias/short_bias (70%/30% configurable)

Direction adjustment logic:
- Short box breakout → bias direction (long_bias/short_bias)
- Mid box breakout → full direction (long/short)
- Long box breakout → emergency handling (unchanged)
- Recovery: long → long_bias → neutral ← short_bias ← short

Config options:
- EnableDirectionAdjust (default: false)
- DirectionBiasRatio (default: 0.7)

Includes unit tests for all direction-related functions.

store/strategy.go

@@ -81,6 +81,10 @@ type GridStrategyConfig struct {
 	DailyLossLimitPct float64 `json:"daily_loss_limit_pct"`
 	// Use maker-only orders for lower fees
 	UseMakerOnly bool `json:"use_maker_only"`
+	// Enable automatic grid direction adjustment based on box breakouts
+	EnableDirectionAdjust bool `json:"enable_direction_adjust"`
+	// Direction bias ratio for long_bias/short_bias modes (default 0.7 = 70%/30%)
+	DirectionBiasRatio float64 `json:"direction_bias_ratio"`
 }
 
 // PromptSectionsConfig editable sections of System Prompt