refactor: delete duplicate RetryStrategy from trading_engine

The RetryStrategy enum in trading_engine/src/types/error.rs was an exact
duplicate of common::error::RetryStrategy with zero callers in the crate.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/trading_engine/src/types/error.rs

@@ -1,88 +1,7 @@
 //! Error module for Foxhunt HFT system.
 
-// Removed pub use - import errors directly where needed
-
-use std::fmt;
-use std::time::Duration;
-
-use serde::{Deserialize, Serialize};
-
-// Note: ErrorSeverity moved to error-handling crate to avoid duplication
-
-// Note: ErrorSeverity Display impl moved to error-handling crate
-
-/// Retry strategies for error recovery with exponential backoff
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-/// RetryStrategy component.
-pub enum RetryStrategy {
-    /// Do not retry - error is permanent
-    NoRetry,
-    /// Retry immediately without delay
-    Immediate,
-    /// Linear backoff with fixed intervals
-    Linear {
-        /// Base delay in milliseconds between retries
-        base_delay_ms: u64,
-    },
-    /// Exponential backoff with jitter
-    Exponential {
-        /// Base delay in milliseconds for exponential backoff
-        base_delay_ms: u64,
-        /// Maximum delay cap in milliseconds
-        max_delay_ms: u64,
-    },
-    /// Wait for circuit breaker to close
-    CircuitBreaker,
-}
-
-impl RetryStrategy {
-    /// Calculate delay for retry attempt with jitter to prevent thundering herd
-    #[must_use]
-    pub fn calculate_delay(&self, attempt: u32) -> Option<Duration> {
-        match self {
-            Self::NoRetry => None,
-            Self::Immediate => Some(Duration::from_millis(0)),
-            Self::Linear { base_delay_ms } => {
-                Some(Duration::from_millis(base_delay_ms * u64::from(attempt)))
-            }
-            Self::Exponential {
-                base_delay_ms,
-                max_delay_ms,
-            } => {
-                let delay_ms = base_delay_ms * 2_u64.pow(attempt.min(10));
-                let capped_delay = delay_ms.min(*max_delay_ms);
-
-                // Add jitter to prevent thundering herd (±10%)
-                // Use float division for precise calculation, then convert back to int
-                #[allow(
-                    clippy::cast_possible_truncation,
-                    clippy::cast_sign_loss,
-                    clippy::cast_precision_loss
-                )]
-                // Safe: round() ensures valid range, precision loss is acceptable for jitter calculation
-                let jitter = (((capped_delay as f64) * 0.1).round() as u64).max(1);
-                let jittered_delay =
-                    capped_delay.saturating_sub(jitter) + (jitter * 2).saturating_div(2); // Simple deterministic jitter replacement
-
-                Some(Duration::from_millis(jittered_delay))
-            }
-            Self::CircuitBreaker => Some(Duration::from_secs(30)),
-        }
-    }
-
-    /// Get maximum recommended retry attempts for this strategy
-    #[must_use]
-    pub const fn max_attempts(&self) -> Option<u32> {
-        match self {
-            Self::NoRetry => Some(0),
-            Self::Immediate => Some(3),
-            Self::Linear { .. } => Some(5),
-            Self::Exponential { .. } => Some(7),
-            Self::CircuitBreaker => Some(1),
-        }
-    }
-}
+// Error types and conversions for trading_engine.
+// ErrorSeverity and RetryStrategy live in the common crate.
 
 // ===== EXTERNAL ERROR CONVERSIONS =====