fix: resolve diagnostic paths under the base path prefix and tolerate health-style ping responses

backend/test/workspaces-diagnostics.test.ts

@@ -9,7 +9,7 @@ import {
   type DiagnosticAdapters,
 } from "../src/workspaces/diagnostics.js";
 import type { RuntimeBindings } from "../src/workspaces/runtime-renderer.js";
-import { parseWorkspaceYaml } from "../src/workspaces/schema.js";
+import { parseWorkspaceYaml, resolveDiagnosticUrl } from "../src/workspaces/schema.js";
 
 const workspace = parseWorkspaceYaml(`workspace:
   schema_version: 3
@@ -486,3 +486,10 @@ test("classifies an observed non-cosine Qdrant distance as semantic incompatibil
     code: "connector_unavailable",
   }));
 });
+
+test("resolveDiagnosticUrl appends the path to a base URL with a path prefix", () => {
+  expect(resolveDiagnosticUrl("https://dwh.example.test/dwh/", "/rpc/ping").toString())
+    .toBe("https://dwh.example.test/dwh/rpc/ping");
+  expect(resolveDiagnosticUrl("https://dwh.example.test/dwh", "/rpc/ping").toString())
+    .toBe("https://dwh.example.test/dwh/rpc/ping");
+});