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/vitest.config.ts

@@ -0,0 +1,17 @@
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { defineConfig } from 'vitest/config';
+import { vitestSharedPaths } from '../../vitest.shared.mts';
+
+const dirname = path.dirname(fileURLToPath(import.meta.url));
+const { projectResolve } = vitestSharedPaths(dirname);
+
+export default defineConfig({
+  resolve: projectResolve,
+  test: {
+    globals: false,
+    environment: 'node',
+    include: ['__tests__/**/*.test.ts'],
+    testTimeout: 15000,
+  },
+});