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/tui/src/components/SelectableItem.tsx

@@ -0,0 +1,22 @@
+import React from "react";
+import { Box, Text } from "ink";
+
+/** Renders a selectable item: ▶ + space when selected, space + space when not. Fixed width to prevent layout shift. */
+export function SelectableItem({
+  isSelected,
+  bold,
+  children,
+}: {
+  isSelected: boolean;
+  bold?: boolean;
+  children: React.ReactNode;
+}) {
+  return (
+    <Box flexShrink={0} flexDirection="row">
+      <Box width={2}>
+        <Text bold={bold}>{isSelected ? "▶ " : "  "}</Text>
+      </Box>
+      <Text bold={bold}>{children}</Text>
+    </Box>
+  );
+}