fix: dashboard errors — Math.abs, API routing, fetchHistorical guard

Fixes three bugs in dashboard:

1. vbt.html: bare abs(dd) → Math.abs(dd) — fixes ReferenceError
2. server.py: Add /cv/ routing for Next.js quant dashboard
   - Mount _next static assets at /cv/_next (not /cv/ which eats API routes)
   - Add /cv/api/* routes for backtests/historical, detail, recalc, risk
   - Add /cv/ws WebSocket endpoints for live/paper metrics
   - Add /cv/ catchall for Next.js HTML pages
3. dashboard-next/src/lib/api.ts: add res.ok guard to fetchHistorical()
   — prevents SyntaxError when API returns HTML error pages
4. sim/maker.py: guard observe() against zero mid_price

dashboard/server.py

@@ -202,6 +202,18 @@ async def paper_websocket_endpoint(websocket: WebSocket):
 async def get_metrics_rest():
     return JSONResponse(read_metrics())
 
+@app.get("/api/metrics/v2")
+async def get_metrics_v2():
+    """Read the v2 node metrics file."""
+    try:
+        v2_file = "/tmp/ftdt-metrics-v2.json"
+        if os.path.exists(v2_file):
+            with open(v2_file) as f:
+                return JSONResponse(json.load(f))
+    except (json.JSONDecodeError, IOError):
+        pass
+    return JSONResponse({"status": "no_data"})
+
 @app.get("/api/metrics/paper")
 async def get_paper_metrics_rest():
     return JSONResponse(read_paper_metrics())
@@ -903,10 +915,70 @@ def main():
 
 
 
-# Serve Next.js assets at /_next/static/
-_next_dir = Path(__file__).parent / "static" / "_next"
-if _next_dir.is_dir():
-    app.mount("/_next", StaticFiles(directory=str(_next_dir)), name="next_assets")
+# ── Next.js Dashboard (served at /cv/) ──────────────────────
+
+
+@app.get("/cv/api/backtests/historical")
+async def cv_historical_backtests():
+    return await list_historical_backtests()
+
+@app.get("/cv/api/backtest/historical/{name}")
+async def cv_historical_detail(name: str):
+    return await get_historical_backtest(name)
+
+@app.get("/cv/api/backtest/{name}")
+async def cv_backtest_detail(name: str):
+    return await get_backtest(name)
+
+@app.get("/cv/api/backtest/{name}/recalc")
+async def cv_backtest_recalc(name: str, fee_tier: int = 0, staking_tier: str = "none"):
+    return await recalc_backtest(name, fee_tier, staking_tier)
+
+@app.get("/cv/api/risk")
+async def cv_risk():
+    return await get_risk_metrics()
+
+@app.websocket("/cv/ws")
+async def cv_websocket(websocket):
+    await websocket_endpoint(websocket)
+
+@app.websocket("/cv/ws/paper")
+async def cv_paper_websocket(websocket):
+    await paper_websocket_endpoint(websocket)
+
+@app.get("/cv/api/metrics/v2")
+async def cv_metrics_v2():
+    return await get_metrics_v2()
+
+
+# Mount Next.js static assets only (not the whole /cv/ path)
+_next_out = Path(__file__).parent.parent / "dashboard-next" / "out"
+_next_static = _next_out / "_next" if _next_out.is_dir() else None
+if _next_static and _next_static.is_dir():
+    app.mount("/cv/_next", StaticFiles(directory=str(_next_static)), name="cv_static")
+
+# Serve Next.js HTML pages individually
+_serve_next_static = _next_out.is_dir()
+@app.get("/cv")
+async def cv_index():
+    if _serve_next_static:
+        return FileResponse(_next_out / "index.html")
+    return FileResponse(STATIC_DIR / "index.html")
+
+@app.get("/cv/{path:path}")
+async def cv_catchall(path: str):
+    if _serve_next_static:
+        fpath = _next_out / path
+        if fpath.is_file():
+            return FileResponse(fpath)
+        if (fpath / "index.html").is_file():
+            return FileResponse(fpath / "index.html")
+        # Try .html extension
+        html_path = _next_out / f"{path}.html"
+        if html_path.is_file():
+            return FileResponse(html_path)
+    return FileResponse(STATIC_DIR / "index.html")
+
 
 if __name__ == "__main__":
     main()

dashboard/static/vbt.html

@@ -236,7 +236,7 @@ function renderDetail(r){
   const wr=(r.win_rate??0)*100,pf=r.profit_factor??0,eq=r.end_equity??10000;
   const tr=r.total_trades??0,nb=r.n_bars??0,so=r.sortino??0;
   const asset=r.asset||'-';const params=r.params||{};
-  const calmar=r.calmar||((dd)?(ret/abs(dd)):0);
+  const calmar=r.calmar||((dd)?(ret/Math.abs(dd)):0);
   const expec=r.expectancy??(tr?(r.pnl??0)/tr:0);
 
   let avgDur='';