feat(server,web,desktop): admin "use system HTTP proxy" switch (#225)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

packages/server/test/proxy.test.ts

@@ -0,0 +1,51 @@
+/**
+ * Unit tests for the outbound-proxy module's pure parts: the NO_PROXY loopback merge
+ * and the dispatcher choice per switch state. No real network and no global install —
+ * installGlobalProxyDispatcher (fetch replacement) runs only in the production entry.
+ */
+import { describe, expect, it } from "vitest";
+import { Agent, EnvHttpProxyAgent } from "undici";
+import { buildProxyDispatcher, mergedNoProxy } from "../src/net/proxy.js";
+
+describe("mergedNoProxy", () => {
+  it("yields exactly the loopback names when the environment has no NO_PROXY", () => {
+    expect(mergedNoProxy({})).toBe("localhost,127.0.0.1,::1");
+  });
+
+  it("appends the loopback names after the environment's entries", () => {
+    expect(mergedNoProxy({ NO_PROXY: "example.com,.corp.internal" })).toBe(
+      "example.com,.corp.internal,localhost,127.0.0.1,::1",
+    );
+  });
+
+  it("prefers the lowercase spelling, like undici itself", () => {
+    expect(mergedNoProxy({ no_proxy: "a.example", NO_PROXY: "b.example" })).toBe(
+      "a.example,localhost,127.0.0.1,::1",
+    );
+  });
+
+  it("does not duplicate loopback names already present (case-insensitively)", () => {
+    expect(mergedNoProxy({ NO_PROXY: "LOCALHOST,::1" })).toBe("LOCALHOST,::1,127.0.0.1");
+  });
+
+  it("survives messy separators (comma/whitespace mix, empty segments)", () => {
+    expect(mergedNoProxy({ NO_PROXY: " example.com ,, other.example " })).toBe(
+      "example.com,other.example,localhost,127.0.0.1,::1",
+    );
+  });
+});
+
+describe("buildProxyDispatcher", () => {
+  it("on → EnvHttpProxyAgent (proxy env honored), off → plain Agent (direct)", async () => {
+    const on = buildProxyDispatcher(true, {});
+    const off = buildProxyDispatcher(false, {});
+    try {
+      expect(on).toBeInstanceOf(EnvHttpProxyAgent);
+      expect(off).toBeInstanceOf(Agent);
+      expect(off).not.toBeInstanceOf(EnvHttpProxyAgent);
+    } finally {
+      await on.close();
+      await off.close();
+    }
+  });
+});