Add JoinQuant comparison plugin

plugins/joinquant/README.md

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+# JoinQuant Comparison Plugin
+
+This plugin exports frozen targets from the internal A-share research pipeline,
+drives a standalone JoinQuant wrapper strategy, ingests JoinQuant output files,
+and reconciles them against the internal reference simulator.
+
+The plugin validates system mechanics, not alpha quality:
+
+- date alignment
+- symbol mapping
+- target position generation
+- open execution timing
+- lot rounding and filled shares
+- position carry
+- trading cost and PnL accounting
+- blocked trades from suspension and price limits
+
+## Commands
+
+```bash
+uv run python cli.py joinquant export-targets \
+  --positions-path portfolio/run1.pq \
+  --portfolio-name run1 \
+  --mode target_shares \
+  --start-date 2026-07-01 \
+  --end-date 2026-07-31 \
+  --out-dir plugins_output/joinquant/targets
+
+uv run python cli.py joinquant write-wrapper \
+  --portfolio-name run1 \
+  --mode target_shares \
+  --out-path plugins_output/joinquant/wrapper_strategy_run1.py
+
+uv run python cli.py joinquant ingest \
+  --portfolio-name run1 \
+  --fills-csv path/to/jq_fills.csv \
+  --positions-csv path/to/jq_positions.csv \
+  --pnl-csv path/to/jq_pnl.csv \
+  --out-dir plugins_output/joinquant/ingested
+
+uv run python cli.py joinquant reconcile \
+  --portfolio-name run1 \
+  --targets-dir plugins_output/joinquant/targets/run1 \
+  --our-fills-path fills/run1.pq \
+  --our-positions-path portfolio/run1.pq \
+  --our-pnl-path pnl/run1.pq \
+  --jq-fills-path plugins_output/joinquant/ingested/run1/fills.pq \
+  --jq-positions-path plugins_output/joinquant/ingested/run1/positions.pq \
+  --jq-pnl-path plugins_output/joinquant/ingested/run1/pnl.pq \
+  --out-dir plugins_output/joinquant/reconcile
+```
+
+`target_shares` is the default and uses the built integer `position_shares`
+from `portfolio build`, matching what the internal simulator executes.
+