feat(FN-3594): split TaskDetailModal test monolith and improve mobile chat/

The merge brings TaskDetailModal test coverage in line with the project's testing standards by splitting the monolithic 6,745-line test file into five focused suites. It also delivers merger reliability improvements including headline-step subject preference, redundant-merge verification skipping, a

Fusion-Task-Id: FN-3594

scripts/__tests__/multi-project-sequencing-doc.test.mjs

@@ -0,0 +1,29 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+const docPath = path.resolve(__dirname, "../../docs/multi-project-sequencing.md");
+const doc = readFileSync(docPath, "utf8");
+
+test("multi-project sequencing note exists with required section headings", () => {
+  const headings = [
+    "## Foundational layer",
+    "## Identity model",
+    "## Recommended sequencing",
+    "## Risks of out-of-order execution",
+  ];
+
+  for (const heading of headings) {
+    assert.ok(doc.includes(heading), `Missing heading: ${heading}`);
+  }
+});
+
+test("multi-project sequencing note references required task IDs", () => {
+  for (const taskId of ["FN-3448", "FN-3449", "FN-3503", "FN-3182"]) {
+    assert.ok(doc.includes(taskId), `Expected reference to ${taskId}`);
+  }
+});