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/hooks/useSelectableList.ts

@@ -0,0 +1,61 @@
+import { useState, useEffect, useCallback } from "react";
+
+function clampFirstVisible(
+  first: number,
+  selected: number,
+  visibleCount: number,
+): number {
+  if (selected < first) return selected;
+  if (selected >= first + visibleCount) return selected - visibleCount + 1;
+  return first;
+}
+
+export interface UseSelectableListOptions {
+  /** When this reference changes, reset selection to 0 (e.g. tools list when switching servers) */
+  resetWhen?: unknown;
+}
+
+/**
+ * Manages selection and scroll position for a virtualized list.
+ * Returns selection state and a setSelection that updates both
+ * selectedIndex and firstVisible so the selected item stays in view.
+ */
+export function useSelectableList(
+  itemCount: number,
+  visibleCount: number,
+  options?: UseSelectableListOptions,
+) {
+  const [selectedIndex, setSelectedIndex] = useState(0);
+  const [firstVisible, setFirstVisible] = useState(0);
+
+  const setSelection = useCallback(
+    (newIndex: number) => {
+      setSelectedIndex(newIndex);
+      setFirstVisible((prev) =>
+        clampFirstVisible(prev, newIndex, visibleCount),
+      );
+    },
+    [visibleCount],
+  );
+
+  // Reset when the list reference changes (e.g. different server).
+  useEffect(() => {
+    if (options?.resetWhen !== undefined) {
+      setSelectedIndex(0);
+      setFirstVisible(0);
+    }
+  }, [options?.resetWhen]);
+
+  // Clamp when list shrinks
+  useEffect(() => {
+    if (itemCount > 0 && selectedIndex >= itemCount) {
+      const newIndex = itemCount - 1;
+      setSelectedIndex(newIndex);
+      setFirstVisible((prev) =>
+        clampFirstVisible(prev, newIndex, visibleCount),
+      );
+    }
+  }, [itemCount, selectedIndex, visibleCount]);
+
+  return { selectedIndex, firstVisible, setSelection };
+}