Replace findings list with a tree; filter ESD/PI false positives.

PE-ESD-001 only on J* connector–IC nets (skip NC, unconnected, VSYS/GND/3V3).
PE-PI-001 treats any capacitor on the rail, including KiCad slash prefixes, as
decoupling. Sort findings ERROR then WARNING then INFO, then RULE/RISK/REVIEW/INFO.
Report sidebar is a collapsed expand-on-click tree instead of an all-open list.
GET /report and complete_findings fail-soft and sort the same way.

backend/routers/reports.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import json
+import logging
 import re
 import uuid
 from datetime import datetime, timezone
@@ -15,6 +16,7 @@ from backend.periscopex.finding_engine import (
     apply_decisions,
     complete_findings,
     decision_from_review,
+    sort_findings,
     upsert_decision,
 )
 from backend.periscopex.models import Finding
@@ -30,6 +32,7 @@ from backend.routers.deps import get_storage, get_user_id, resolve_or_404
 from backend.services import projects as proj_svc
 
 router = APIRouter(tags=["reports"])
+log = logging.getLogger(__name__)
 
 # Allow alphanumeric, dash, underscore, dot, colon, forward-slash, plus, hash, space
 _SAFE_MPN = re.compile(r"^[A-Za-z0-9][A-Za-z0-9_\-\.:/ +#,()]*$")
@@ -56,7 +59,11 @@ async def get_report(project_id: str, request: Request):
     if merged is None:
         raise HTTPException(404, "Report not found — run the pipeline first")
     findings = _findings_from_report(merged)
-    complete_findings(findings)
+    try:
+        complete_findings(findings)
+    except Exception:
+        log.exception("complete_findings failed while serving report %s", project_id)
+        sort_findings(findings)
     dec_key = f"{prefix}/decisions.json"
     if storage.exists(dec_key):
         try:
@@ -158,7 +165,7 @@ def _findings_from_report(report_data: dict) -> list[Finding]:
         try:
             out.append(Finding.model_validate(raw))
         except Exception:
-            continue
+            log.warning("Skipping malformed finding in report", exc_info=True)
     return out