feat(dashboard): surface failing requests so admins see dropped traffic

docs/dashboard.md

@@ -157,6 +157,10 @@ gateway.
 
 - **Activity**: the per-request log of what the gateway served, with filters.
   Use it to inspect individual requests, their models, and their outcomes.
+  Requests the gateway refused are logged too, so filtering to the `error`
+  status shows what is being dropped, including requests rejected for having no
+  pricing under `require_pricing`. Diagnostic detail stays in the gateway logs
+  rather than the browser.
 - **Usage**: aggregate usage and analytics, showing spend and volume over time,
   broken down by model and by user.
 

src/gateway/api/routes/_passthrough.py

@@ -219,9 +219,28 @@ async def run_passthrough(
             and pricing_required_but_missing(pricing, require_pricing=config.require_pricing)
         ):
             await refund_reservation(db, reservation)
+            no_pricing_detail = no_pricing_error_detail(model)
+            # Record the rejection so dropped traffic is visible in the activity
+            # log and countable as an error, rather than only reaching the
+            # operator as a user complaint. cost stays null: nothing was spent.
+            await log_writer.put(
+                UsageLog(
+                    id=str(uuid.uuid4()),
+                    api_key_id=api_key_id,
+                    user_id=user_id,
+                    timestamp=datetime.now(UTC),
+                    model=resolved.model,
+                    provider=resolved.instance,
+                    endpoint=endpoint,
+                    status="error",
+                    error_message=no_pricing_detail,
+                    latency_ms=_elapsed_ms(started_at),
+                    counts_toward_budget=not budget_exempt,
+                )
+            )
             raise HTTPException(
                 status_code=status.HTTP_402_PAYMENT_REQUIRED,
-                detail=no_pricing_error_detail(model),
+                detail=no_pricing_detail,
             )
 
     # Model access control (per-key). The reservation is already taken above (the

src/gateway/api/routes/_pipeline.py

@@ -710,9 +710,28 @@ async def resolve_request_context(
         # cost=null when unpriced.
         if not budget_exempt and pricing_required_but_missing(gate_pricing, require_pricing=config.require_pricing):
             await refund_reservation(db, reservation)
+            no_pricing_detail = no_pricing_error_detail(model)
+            # Record the rejection before raising. Gateway-side rejections used to
+            # leave no trace, so an operator who flipped require_pricing on had no
+            # way to see that live traffic was being dropped (only a user complaint
+            # would tell them). The row carries cost=null: nothing was spent, so it
+            # never affects spend or the budget, it just makes the drop visible in
+            # the activity log and countable as an error.
+            await log_usage(
+                db=db,
+                log_writer=log_writer,
+                api_key_id=api_key_id,
+                model=model,
+                provider=gate_instance,
+                endpoint=adapter.endpoint,
+                user_id=user_id,
+                error=no_pricing_detail,
+                latency_ms=_elapsed_ms(started_at),
+                counts_toward_budget=not budget_exempt,
+            )
             raise adapter.error(
                 402,
-                no_pricing_error_detail(model),
+                no_pricing_detail,
                 ErrorKind.INVALID_REQUEST,
             )