refactor(bias-audit): simplify based on code review

- Run PDF generation on a threadpool via asyncio.to_thread() so ReportLab
  does not block the FastAPI event loop during concurrent downloads.
- Drop the duplicated metadata fields (aedt_name, description,
  data_source_description) in the run request. The modal already writes
  the top-level systemName/systemDescription/dataSource fields, and the
  report generator reads those directly. The metadata dict now only
  carries distribution_date, which has no top-level counterpart.
- Reuse the existing triggerBrowserDownload helper from
  browserDownload.utils instead of rolling a new blob-download pattern
  in BiasAuditDetail.tsx. Applies to both JSON and PDF downloads.

Author: gorkem-bwl

Clients/src/presentation/pages/EvalsDashboard/BiasAuditDetail.tsx

@@ -6,6 +6,7 @@ import { StatCard } from "../../components/Cards/StatCard";
 import { CustomizableButton } from "../../components/button/customizable-button";
 import { getStatusChip, getModeChip } from "./biasAuditHelpers";
 import ConfirmationModal from "../../components/Dialogs/ConfirmationModal";
+import { triggerBrowserDownload } from "../../utils/browserDownload.utils";
 import { palette } from "../../themes/palette";
 import {
   getBiasAuditResults,
@@ -311,14 +312,7 @@ export default function BiasAuditDetail({ auditId, onBack }: BiasAuditDetailProp
     try {
       const json = JSON.stringify(audit.results, null, 2);
       const blob = new Blob([json], { type: "application/json" });
-      const url = URL.createObjectURL(blob);
-      const a = document.createElement("a");
-      a.href = url;
-      a.download = `bias-audit-${auditId}.json`;
-      document.body.appendChild(a);
-      a.click();
-      document.body.removeChild(a);
-      URL.revokeObjectURL(url);
+      triggerBrowserDownload(blob, `bias-audit-${auditId}.json`);
     } catch (err) {
       console.error("Failed to download results:", err);
     }
@@ -329,14 +323,7 @@ export default function BiasAuditDetail({ auditId, onBack }: BiasAuditDetailProp
     setIsDownloadingPdf(true);
     try {
       const blob = await downloadBiasAuditReport(auditId);
-      const url = URL.createObjectURL(blob);
-      const a = document.createElement("a");
-      a.href = url;
-      a.download = `bias-audit-${auditId}.pdf`;
-      document.body.appendChild(a);
-      a.click();
-      document.body.removeChild(a);
-      URL.revokeObjectURL(url);
+      triggerBrowserDownload(blob, `bias-audit-${auditId}.pdf`);
     } catch (err) {
       console.error("Failed to download PDF report:", err);
     } finally {
@@ -368,7 +355,7 @@ export default function BiasAuditDetail({ auditId, onBack }: BiasAuditDetailProp
           <ArrowLeft size={18} color={theme.palette.text.secondary} strokeWidth={1.5} />
         </Box>
         <Stack spacing={0.5} flex={1}>
-          <Stack direction="row" alignItems="center" spacing={1.5}>
+          <Stack direction="row" alignItems="center" sx={{ gap: "8px" }}>
             <Typography sx={{ fontSize: 15, fontWeight: 600, color: theme.palette.text.primary }}>
               {audit?.presetName || "Bias audit"}
             </Typography>
@@ -381,7 +368,7 @@ export default function BiasAuditDetail({ auditId, onBack }: BiasAuditDetailProp
             </Typography>
           )}
         </Stack>
-        <Stack direction="row" spacing={1}>
+        <Stack direction="row" sx={{ gap: "8px" }}>
           {audit?.results && status === "completed" && (
             <CustomizableButton
               variant="contained"

Clients/src/presentation/pages/EvalsDashboard/NewBiasAuditModal.tsx

@@ -343,10 +343,7 @@ const NewBiasAuditModal: React.FC<NewBiasAuditModalProps> = ({
         systemDescription: aedtDescription,
         dataSource: dataSourceDescription,
         metadata: {
-          aedt_name: aedtName,
-          description: aedtDescription,
           distribution_date: distributionDate,
-          data_source_description: dataSourceDescription,
         },
       };
       const result = await runBiasAudit(csvFile, config);

EvalServer/src/controllers/bias_audits.py

@@ -5,6 +5,7 @@
 status polling, and result retrieval.
 """
 
+import asyncio
 import json
 import logging
 import traceback
@@ -419,7 +420,8 @@ async def get_bias_audit_report_controller(
 
     from engines.bias_audit.report_generator import generate_pdf_report
     try:
-        pdf_bytes = generate_pdf_report(audit)
+        # PDF rendering is CPU-bound and holds the GIL; run off the event loop
+        pdf_bytes = await asyncio.to_thread(generate_pdf_report, audit)
     except Exception as e:
         logger.error(f"[BiasAudit] Failed to generate report for {audit_id}: {e}")
         logger.error(traceback.format_exc())

EvalServer/src/engines/bias_audit/report_generator.py

@@ -159,7 +159,7 @@ def _cover_page(
     config = audit.get("config", {}) or {}
     results = audit.get("results", {}) or {}
 
-    system_name = config.get("systemName") or config.get("metadata", {}).get("aedt_name") or "AI system"
+    system_name = config.get("systemName") or "AI system"
     system_version = config.get("systemVersion") or ""
     preset_name = audit.get("presetName", "Custom")
 
@@ -234,13 +234,12 @@ def _system_description(
     story: list, styles: Dict[str, ParagraphStyle], audit: Dict[str, Any]
 ) -> None:
     config = audit.get("config", {}) or {}
-    meta = config.get("metadata", {}) or {}
 
     story.append(Paragraph("System description", styles["h1"]))
     story.append(_key_value_table([
-        ("Name", config.get("systemName") or meta.get("aedt_name", "")),
+        ("Name", config.get("systemName", "")),
         ("Version", config.get("systemVersion", "")),
-        ("Description", config.get("systemDescription") or meta.get("description", "")),
+        ("Description", config.get("systemDescription", "")),
         ("Deployment context", config.get("deploymentContext", "")),
     ]))
 
@@ -249,7 +248,6 @@ def _data_description(
     story: list, styles: Dict[str, ParagraphStyle], audit: Dict[str, Any]
 ) -> None:
     config = audit.get("config", {}) or {}
-    meta = config.get("metadata", {}) or {}
     results = audit.get("results", {}) or {}
 
     story.append(Paragraph("Data description", styles["h1"]))
@@ -265,7 +263,7 @@ def _data_description(
         date_range = f"up to {end}"
 
     story.append(_key_value_table([
-        ("Source", config.get("dataSource") or meta.get("data_source_description", "")),
+        ("Source", config.get("dataSource", "")),
         ("Date range", date_range),
         ("Total records", _count(results.get("total_applicants"))),
         ("Records with missing data", _count(results.get("unknown_count"))),