Align JoinQuant targets to execution dates

plugins/joinquant/README.md

@@ -22,6 +22,7 @@ uv run python cli.py joinquant export-targets \
   --positions-path portfolio/run1.pq \
   --portfolio-name run1 \
   --mode target_shares \
+  --execution-calendar-path data/daily_bars/csi500 \
   --start-date 2026-07-01 \
   --end-date 2026-07-31 \
   --out-dir plugins_output/joinquant/targets
@@ -52,4 +53,6 @@ uv run python cli.py joinquant reconcile \
 
 `target_shares` is the default and uses the built integer `position_shares`
 from `portfolio build`, matching what the internal simulator executes.
-
+For strict simulator-vs-JoinQuant comparison, pass `--execution-calendar-path`
+so position dates are shifted to the next session open, matching the internal
+simulator's next-open convention.