Make the governed RAG evidence path executable end to end

Separate local parsing from model indexing, bind review decisions to immutable manifests, persist vectors behind active profiles, and expose retrieval, chat, evaluation, and document workflows through the React workbench.

Constraint: Live Bailian authentication currently fails for all three configured capabilities

Rejected: Direct upload-to-embedding flow | bypasses local review and manifest binding

Confidence: high

Scope-risk: broad

Directive: Keep private-data deployment blocked until authentication, RBAC, and separate database roles land

Tested: make verify; fresh and replay Docker document smoke; worker recovery smoke; frozen synthetic evaluation; migration 0003-0004 roundtrip

Not-tested: Successful live Bailian calls, OCR, real multi-user authorization

backend/app/core/problems.py

@@ -6,6 +6,7 @@ from dataclasses import dataclass
 from typing import Any
 
 from fastapi import Request
+from fastapi.exceptions import RequestValidationError
 from fastapi.responses import JSONResponse
 
 PROBLEM_MEDIA_TYPE = "application/problem+json"
@@ -60,3 +61,35 @@ def api_problem_handler(request: Request, exc: ApiProblem) -> JSONResponse:
             trace_id=trace_id,
         ),
     )
+
+
+def request_validation_problem_handler(
+    request: Request,
+    exc: RequestValidationError,
+) -> JSONResponse:
+    """Return bounded validation metadata without echoing rejected input values."""
+
+    trace_id = str(getattr(request.state, "trace_id", "unavailable"))
+    field_errors: list[dict[str, str]] = []
+    for error in exc.errors():
+        location = error.get("loc", ())
+        field = ".".join(str(part) for part in location if str(part) not in {"body", "query"})
+        error_type = error.get("type")
+        field_errors.append(
+            {
+                "field": field[:240] or "request",
+                "code": str(error_type)[:120] if error_type else "invalid_value",
+            }
+        )
+    return JSONResponse(
+        status_code=422,
+        media_type=PROBLEM_MEDIA_TYPE,
+        content=problem_payload(
+            status=422,
+            code="REQUEST_VALIDATION_FAILED",
+            title="Request validation failed",
+            detail="One or more request fields did not satisfy the public API contract.",
+            trace_id=trace_id,
+            field_errors=field_errors[:50],
+        ),
+    )