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/cli/src/index.ts

@@ -0,0 +1,19 @@
+#!/usr/bin/env node
+
+import { resolve } from "path";
+import { fileURLToPath } from "url";
+import { runCli, validLogLevels } from "./cli.js";
+import { handleError } from "./error-handler.js";
+
+export { runCli, validLogLevels };
+
+const __filename = fileURLToPath(import.meta.url);
+const isMain =
+  process.argv[1] !== undefined &&
+  resolve(process.argv[1]) === resolve(__filename);
+
+if (isMain) {
+  runCli(process.argv)
+    .then(() => process.exit(0))
+    .catch(handleError);
+}