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/launcher/src/index.ts

@@ -0,0 +1,64 @@
+#!/usr/bin/env node
+
+import { dirname, join } from "node:path";
+import { fileURLToPath, pathToFileURL } from "node:url";
+import { Command } from "commander";
+import { parseLauncherArgv } from "./parse-launcher-argv.js";
+
+const launcherDir = dirname(fileURLToPath(import.meta.url));
+
+function clientEntry(client: "web" | "cli" | "tui"): string {
+  return pathToFileURL(
+    join(launcherDir, "..", "..", client, "build", "index.js"),
+  ).href;
+}
+
+const program = new Command();
+
+program
+  .name("mcp-inspector")
+  .description("MCP Inspector – run web UI, CLI, or TUI")
+  .option("--web", "Run web UI (default)")
+  .option("--cli", "Run CLI")
+  .option("--tui", "Run TUI");
+
+let parsedArgv;
+try {
+  parsedArgv = parseLauncherArgv(process.argv);
+} catch (err) {
+  const message =
+    err instanceof Error ? err.message : "Invalid launcher arguments.";
+  console.error(`Error: ${message}`);
+  process.exit(1);
+}
+
+const { mode, forwardedArgv, hasPrefixModeFlag } = parsedArgv;
+
+const helpOnly =
+  process.argv.includes("-h") || process.argv.includes("--help");
+
+if (helpOnly && !hasPrefixModeFlag) {
+  program.outputHelp();
+  console.log(
+    "\nMode flags (--web, --cli, --tui) must appear before app options. All following arguments are forwarded unchanged.",
+  );
+  process.exit(0);
+}
+
+async function run(): Promise<void> {
+  if (mode === "web") {
+    const { runWeb } = await import(clientEntry("web"));
+    await runWeb(forwardedArgv);
+  } else if (mode === "cli") {
+    const { runCli } = await import(clientEntry("cli"));
+    await runCli(forwardedArgv);
+  } else {
+    const { runTui } = await import(clientEntry("tui"));
+    await runTui(forwardedArgv);
+  }
+}
+
+run().catch((err: unknown) => {
+  console.error("Error running MCP Inspector:", err);
+  process.exit(1);
+});

clients/launcher/src/parse-launcher-argv.ts

@@ -0,0 +1,43 @@
+export const LAUNCHER_MODE_FLAGS = new Set(["--web", "--cli", "--tui"]);
+
+export type LauncherMode = "web" | "cli" | "tui";
+
+export type ParseLauncherArgvResult = {
+  mode: LauncherMode;
+  forwardedArgv: string[];
+  hasPrefixModeFlag: boolean;
+};
+
+/**
+ * Launcher mode flags are read only from a contiguous prefix of user args
+ * (argv[2…]). Everything after the first non-mode token is forwarded
+ * unchanged so values like `--cli` can appear in app/server config.
+ */
+export function parseLauncherArgv(argv: string[]): ParseLauncherArgvResult {
+  const executable = argv.slice(0, 2);
+  const userArgs = argv.slice(2);
+
+  const prefixFlags: string[] = [];
+  let index = 0;
+  while (index < userArgs.length && LAUNCHER_MODE_FLAGS.has(userArgs[index]!)) {
+    prefixFlags.push(userArgs[index]!);
+    index++;
+  }
+
+  if (prefixFlags.length > 1) {
+    throw new Error("Specify at most one of --web, --cli, or --tui.");
+  }
+
+  const mode: LauncherMode =
+    prefixFlags[0] === "--tui"
+      ? "tui"
+      : prefixFlags[0] === "--cli"
+        ? "cli"
+        : "web";
+
+  return {
+    mode,
+    forwardedArgv: [...executable, ...userArgs.slice(index)],
+    hasPrefixModeFlag: prefixFlags.length > 0,
+  };
+}