feat: consolidate database management work

Add catalog-owned logical relationships and runtime snapshots, extend the database-management UI and validation coverage, and document the updated operational workflow.

Keep active sensitive-generation status in a tooltip and indicator, and update the layout E2E to follow the history action in its new database-scoped location.

backend/test/routes-sessions.test.ts

@@ -517,6 +517,63 @@ test("creates a session from the active immutable workspace revision", async ()
   }));
 });
 
+test("hands one effective relationship snapshot to both retrieval and Pi", async () => {
+  const effective = JSON.stringify({
+    schemaVersion: 1,
+    workspaceId: "default",
+    relationships: [],
+  });
+  const render = vi.fn(async () => effective);
+  const acquireWorkspaceRuntime = vi.fn((_workspace: string, relationships?: string) => ({
+    path: "/runtime/with-relationships.yaml",
+    workspaceId: "default",
+    workspaceRevision: "e".repeat(40),
+    release: vi.fn(),
+  }));
+  const searchPack = vi.fn(async () => {});
+  const createFor = vi.fn(() => ({ bridge: { onClientEvent: () => {} } }));
+  const app = buildApp(loadConfig({ THT_HARNESS_DIR: "../harness" }), {
+    thtRunner: {
+      sessionNew: async () => ({ id: "effective-map" }),
+      acquireWorkspaceRuntime,
+      searchPack,
+    } as any,
+    effectiveRelationshipSnapshotProvider: { render } as any,
+    readiness: { ensure: async () => ({ ok: true }) } as any,
+    mgr: {
+      get: () => undefined,
+      createFor,
+      configure: async () => {},
+      start: () => {},
+    } as any,
+    getSettings: () => ({ workspace: "default", thinking: "low" }) as any,
+  });
+
+  const response = await app.inject({
+    method: "POST",
+    url: "/sessions",
+    payload: { question: "Which users placed orders?", workspaceId: "default" },
+  });
+
+  expect(response.statusCode).toBe(200);
+  expect(render).toHaveBeenCalledWith("default");
+  expect(acquireWorkspaceRuntime).toHaveBeenCalledWith(
+    expect.stringContaining("/default.yaml"),
+    effective,
+  );
+  expect(createFor).toHaveBeenCalledWith(
+    "effective-map",
+    expect.objectContaining({
+      runtimeConfig: expect.objectContaining({ path: "/runtime/with-relationships.yaml" }),
+    }),
+  );
+  expect(searchPack).toHaveBeenCalledWith(
+    "Which users placed orders?",
+    "effective-map",
+    "/runtime/with-relationships.yaml",
+  );
+});
+
 test("rejects an SSH-only workspace before persisting or starting a session", async () => {
   const sessionNew = vi.fn(async () => ({ id: "must-not-exist" }));
   const ensure = vi.fn(async () => ({ ok: true }));