feat: port CLI, TUI, and launcher from v1.5 into v2 (#1452)

Ports the CLI, TUI, and launcher from v1.5 into v2 behind a single
`mcp-inspector` entrypoint (launcher → web/cli/tui). Includes the
`mcp-inspector --web --dev` launcher fix (Vite alias resolution + prod-server
double-start), the root `postinstall` install cascade with simplified CI, and
spec/AGENTS docs (no-workspaces rationale, Development setup).

Closes #1246.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/web/src/test/integration/server/web-server-config.test.ts

@@ -1,5 +1,6 @@
 import { describe, it, expect, beforeEach, afterEach } from "vitest";
 import {
+  buildWebServerConfig,
   buildWebServerConfigFromEnv,
   printServerBanner,
   webServerConfigToInitialPayload,
@@ -192,6 +193,39 @@ describe("buildWebServerConfigFromEnv", () => {
   });
 });
 
+describe("buildWebServerConfig", () => {
+  it("matches buildWebServerConfigFromEnv when initialMcpConfig is omitted", () => {
+    process.env[API_SERVER_ENV_VARS.AUTH_TOKEN] = "shared";
+    expect(buildWebServerConfig()).toEqual(buildWebServerConfigFromEnv());
+    expect(buildWebServerConfig({ initialMcpConfig: null })).toEqual(
+      buildWebServerConfigFromEnv(),
+    );
+  });
+
+  it("preserves a stdio initialMcpConfig while applying shared env defaults", () => {
+    process.env.CLIENT_PORT = "7000";
+    const initialMcpConfig = {
+      type: "stdio" as const,
+      command: "node",
+      args: ["server.js"],
+      cwd: "/srv",
+    };
+    const cfg = buildWebServerConfig({ initialMcpConfig });
+    expect(cfg.port).toBe(7000);
+    expect(cfg.initialMcpConfig).toEqual(initialMcpConfig);
+    expect(cfg.allowedOrigins).toEqual(["http://localhost:7000"]);
+  });
+
+  it("preserves remote transport initialMcpConfig", () => {
+    const initialMcpConfig = {
+      type: "streamable-http" as const,
+      url: "https://example.com/mcp",
+    };
+    const cfg = buildWebServerConfig({ initialMcpConfig });
+    expect(cfg.initialMcpConfig).toEqual(initialMcpConfig);
+  });
+});
+
 describe("webServerConfigToInitialPayload", () => {
   it("returns only defaultEnvironment when initialMcpConfig is null", () => {
     const payload = webServerConfigToInitialPayload(baseConfig());