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/tsup.config.ts

@@ -0,0 +1,23 @@
+import { defineConfig } from 'tsup';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const dirname = path.dirname(fileURLToPath(import.meta.url));
+const repoRoot = path.resolve(dirname, '../..');
+
+export default defineConfig({
+  entry: ['src/index.ts'],
+  format: ['esm'],
+  outDir: 'build',
+  clean: true,
+  sourcemap: true,
+  target: 'node22',
+  platform: 'node',
+  // Bundle core source; leave npm deps external.
+  noExternal: [/^@inspector\/core/],
+  esbuildOptions(options) {
+    options.alias = {
+      '@inspector/core': path.join(repoRoot, 'core'),
+    };
+  },
+});