Make Backtrader an optional extra

README.md

@@ -48,6 +48,13 @@ The env is managed with [uv](https://docs.astral.sh/uv/). `uv sync` builds `.ven
 uv sync
 ```
 
+Backtrader is an optional dependency and is **not used by the current pipeline**.
+Install it only for future experiments or adapter work:
+
+```bash
+uv sync --extra backtrader
+```
+
 ## Quick start
 
 ```bash
@@ -401,6 +408,9 @@ constructed positions, fills/costs, P&L, and target-weight research metrics.
 - [x] **Reference execution simulation** — next-open fills over constructed
   `position_shares`, with suspension, price-limit, volume-cap, transaction-cost,
   and slippage controls.
+- [ ] **Optional Backtrader adapter** — Backtrader is available as the
+  `backtrader` extra for possible future event-driven/broker-style experiments,
+  but it is not part of the current canonical portfolio workflow.
 - [ ] **Forward / paper trading** — run the same construction logic on live
   daily data, track simulated fills and a running P&L without real capital.
 - [ ] **Intraday / microstructure data** — bid/ask prices & sizes, mid-price,