fix(clients): preserve large TOML documents without argument spreads

Fixes #4856

src/application/ClientConfigurationDocument.capacity.test.ts

@@ -0,0 +1,56 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  parseClientConfiguration,
+  serializeClientConfiguration,
+  withClientServers,
+} from "./ClientConfigurationDocument.js";
+
+const registration = { command: "rea", args: ["mcp"] };
+
+describe("TOML configuration source capacity", () => {
+  it("retains a large multiline foreign value inside an inline server table", () => {
+    const note = `first\n${"x\n".repeat(500_000)}last`;
+    const original = `mcp_servers = { other = {command="other",env={NOTE="""${note}"""}}}\n`;
+    const parsed = parseClientConfiguration(original, "toml");
+    const desired = withClientServers(parsed, {
+      ...parsed.servers,
+      rea: registration,
+    });
+    const configured = serializeClientConfiguration(desired, "toml", original);
+    expect(configured).toContain(`NOTE="""${note}"""`);
+    expect(parseClientConfiguration(configured, "toml").document).toEqual(
+      desired,
+    );
+    const removed = serializeClientConfiguration(
+      parsed.document,
+      "toml",
+      configured,
+    );
+    expect(removed).toContain(`NOTE="""${note}"""`);
+    expect(parseClientConfiguration(removed, "toml").document).toEqual(
+      parsed.document,
+    );
+  });
+
+  it("removes only REA from a large multiline Grok disabled-server list", () => {
+    const otherNames = '"other",\n'.repeat(500_000);
+    const original =
+      `disabled_mcp_servers = [\n"rea",\n${otherNames}]\n` +
+      '[mcp_servers.other]\ncommand = "other"\n';
+    const parsed = parseClientConfiguration(original, "grok");
+    const desired = withClientServers(parsed, {
+      ...parsed.servers,
+      rea: registration,
+    });
+    const configured = serializeClientConfiguration(desired, "grok", original);
+    const result = parseClientConfiguration(configured, "grok");
+    expect(result.document.disabled_mcp_servers).toEqual(
+      Array<string>(500_000).fill("other"),
+    );
+    expect(result.servers).toEqual({
+      other: { command: "other" },
+      rea: registration,
+    });
+  });
+});