test: migrate workbench fixtures to persistent event streams

Static fulfilled SSE bodies closed immediately and made ordinary UI cases reconnect. Serve persistent fixture streams, retain outage and cursor recovery coverage, and update legacy approval and investigation assertions for current disclosures and SVG diagrams.

Validation: 12 related browser scenarios, 877 unit tests, type checking, scoped ESLint, and diff checks. Unrelated SCADA replay changes remain outside this commit.

tests/browser/investigation-execution-history.e2e.ts

@@ -1,4 +1,5 @@
 import { expect, test } from "@playwright/test";
+import { mockWorkbenchEventStream } from "./support/mock-workbench-event-stream";
 import type { OperationalTask, OperationalTaskSummary } from "../../src/features/workbench/api/operational-task-client";
 import { mockAgentApi } from "./support/mock-agent-api";
 
@@ -189,7 +190,7 @@ test("调查任务执行记录自动刷新并可创建调试会话追加消息",
     notifications: [],
     generated_at: now
   } }));
-  await page.route("http://server.test/api/v1/workbench/events**", (route) => route.fulfill({ contentType: "text/event-stream", body: ": keepalive\n\n" }));
+  await mockWorkbenchEventStream(page);
   await page.route("http://server.test/api/v1/operational-task-notifications**", (route) => route.fulfill({ json: { items: [], limit: 100, offset: 0, next_offset: null } }));
   await page.route("http://server.test/api/v1/operational-tasks**", (route) => {
     const path = new URL(route.request().url()).pathname;