feat(core): add TickData struct, TimeExit reason, compute_backtest_metrics pub fn

- TickData: parallel tick arrays (timestamps, ltp, bid, ask, buy_qty_delta,
  sell_qty_delta, oi) with len/is_empty helpers; callers must pre-convert
  Zerodha cumulative totals to per-tick deltas before passing
- ExitReason::TimeExit: max hold time exceeded variant for tick backtest
- compute_backtest_metrics: pub free fn wrapping PortfolioEngine::calculate_metrics
  so non-OHLCV strategies can produce identical metrics without duplication

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

src/core/types.rs

@@ -104,6 +104,44 @@ impl OhlcvData {
     }
 }
 
+/// Raw tick data series for tick-level backtesting.
+///
+/// All fields are parallel arrays of length N (one entry per tick).
+/// `buy_qty_delta` and `sell_qty_delta` must be per-tick deltas, not
+/// cumulative session totals — callers are responsible for converting
+/// Zerodha-style running sums before passing them here.
+#[derive(Debug, Clone)]
+pub struct TickData {
+    /// Nanoseconds-since-epoch timestamp for each tick.
+    pub timestamps: Vec<Timestamp>,
+    /// Last traded price at each tick.
+    pub ltp: Vec<Price>,
+    /// Best bid price at each tick (0.0 if unavailable).
+    pub bid: Vec<Price>,
+    /// Best ask price at each tick (0.0 if unavailable).
+    pub ask: Vec<Price>,
+    /// Per-tick buy quantity delta (not cumulative).
+    pub buy_qty_delta: Vec<f64>,
+    /// Per-tick sell quantity delta (not cumulative).
+    pub sell_qty_delta: Vec<f64>,
+    /// Open interest at each tick (0 if unavailable).
+    pub oi: Vec<f64>,
+}
+
+impl TickData {
+    /// Number of ticks.
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.ltp.len()
+    }
+
+    /// Whether the series is empty.
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.ltp.is_empty()
+    }
+}
+
 /// Compiled trading signals from strategy.
 #[derive(Debug, Clone)]
 pub struct CompiledSignals {
@@ -214,6 +252,8 @@ pub enum ExitReason {
     EndOfData,
     /// Option expiry settlement.
     Settlement,
+    /// Max hold time exceeded (tick backtest).
+    TimeExit,
 }
 
 /// Backtest configuration.

src/portfolio/engine.rs

@@ -761,6 +761,25 @@ impl PortfolioEngine {
     }
 }
 
+/// Compute `BacktestMetrics` from pre-built curves and trade list.
+///
+/// Exposed as a standalone function so non-OHLCV strategies (e.g. tick backtest)
+/// can produce identical metrics without duplicating the calculation logic.
+pub fn compute_backtest_metrics(
+    equity_curve: &[f64],
+    drawdown_curve: &[f64],
+    returns: &[f64],
+    trades: &[Trade],
+    initial_capital: f64,
+) -> BacktestMetrics {
+    // Delegate to a throwaway engine instance — avoids duplicating the logic.
+    let engine = PortfolioEngine::new(BacktestConfig {
+        initial_capital,
+        ..Default::default()
+    });
+    engine.calculate_metrics(equity_curve, drawdown_curve, returns, trades, &StreamingMetrics::new())
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;