test(gateway): add tests for trusted-proxy lan binding validation

Add comprehensive tests for gateway runtime config validation:
- Trusted-proxy mode allows lan binding
- Trusted-proxy mode rejects loopback binding
- Trusted-proxy mode requires trustedProxies configured
- Token mode requires token to be set
- Token mode allows lan binding when token is provided

These tests validate the fix for the lan binding validation bug
and prevent regression.

src/gateway/server-runtime-config.test.ts

@@ -0,0 +1,115 @@
+import { describe, expect, it, vi } from "vitest";
+import { resolveGatewayRuntimeConfig } from "./server-runtime-config.js";
+
+describe("resolveGatewayRuntimeConfig", () => {
+  describe("trusted-proxy auth mode", () => {
+    it("should allow lan binding with trusted-proxy auth mode", async () => {
+      const cfg = {
+        gateway: {
+          bind: "lan" as const,
+          auth: {
+            mode: "trusted-proxy" as const,
+            trustedProxy: {
+              userHeader: "x-forwarded-user",
+            },
+          },
+          trustedProxies: ["192.168.1.1"],
+        },
+      };
+
+      const result = await resolveGatewayRuntimeConfig({
+        cfg,
+        port: 18789,
+      });
+
+      expect(result.authMode).toBe("trusted-proxy");
+      expect(result.bindHost).toBe("0.0.0.0");
+    });
+
+    it("should reject loopback binding with trusted-proxy auth mode", async () => {
+      const cfg = {
+        gateway: {
+          bind: "loopback" as const,
+          auth: {
+            mode: "trusted-proxy" as const,
+            trustedProxy: {
+              userHeader: "x-forwarded-user",
+            },
+          },
+          trustedProxies: ["192.168.1.1"],
+        },
+      };
+
+      await expect(
+        resolveGatewayRuntimeConfig({
+          cfg,
+          port: 18789,
+        }),
+      ).rejects.toThrow("gateway auth mode=trusted-proxy makes no sense with bind=loopback");
+    });
+
+    it("should reject trusted-proxy without trustedProxies configured", async () => {
+      const cfg = {
+        gateway: {
+          bind: "lan" as const,
+          auth: {
+            mode: "trusted-proxy" as const,
+            trustedProxy: {
+              userHeader: "x-forwarded-user",
+            },
+          },
+          trustedProxies: [],
+        },
+      };
+
+      await expect(
+        resolveGatewayRuntimeConfig({
+          cfg,
+          port: 18789,
+        }),
+      ).rejects.toThrow(
+        "gateway auth mode=trusted-proxy requires gateway.trustedProxies to be configured",
+      );
+    });
+  });
+
+  describe("token/password auth modes", () => {
+    it("should reject token mode without token configured", async () => {
+      const cfg = {
+        gateway: {
+          bind: "lan" as const,
+          auth: {
+            mode: "token" as const,
+          },
+        },
+      };
+
+      await expect(
+        resolveGatewayRuntimeConfig({
+          cfg,
+          port: 18789,
+        }),
+      ).rejects.toThrow("gateway auth mode is token, but no token was configured");
+    });
+
+    it("should allow lan binding with token", async () => {
+      const cfg = {
+        gateway: {
+          bind: "lan" as const,
+          auth: {
+            mode: "token" as const,
+            token: "test-token-123",
+          },
+        },
+      };
+
+      const result = await resolveGatewayRuntimeConfig({
+        cfg,
+        port: 18789,
+      });
+
+      expect(result.authMode).toBe("token");
+      expect(result.bindHost).toBe("0.0.0.0");
+    });
+  });
+});