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>

core/mcp/node/index.ts

@@ -1,7 +1,9 @@
 export {
   parseKeyValuePair,
   parseHeaderPair,
+  withDefaultConfigPath,
   resolveServerConfigs,
+  resolveLaunchServerConfigs,
   getNamedServerConfigs,
   type ServerConfigOptions,
   type ResolveServerConfigsMode,