fix(showcase): regenerate 18 lockfiles in isolation; switch to npm ci

Lockfiles committed in 8ba692c were generated inside the monorepo
while pnpm's hoisted node_modules tree was present. npm-arborist
resolved transitive deps against pnpm's symlinks and wrote ~40
`../../../node_modules/.pnpm/...` paths into each lockfile's
`packages` map.

npm 10 can parse the JSON, but its arborist bombs out walking the
tree at those pnpm-relative entries with the misleading error:

    npm error code EUSAGE
    npm error The `npm ci` command can only install with an
    npm error existing package-lock.json or npm-shrinkwrap.json
    npm error with lockfileVersion >= 1.

`npm install --dry-run` surfaces the real cause:

    Cannot read properties of undefined (reading 'extraneous')

A fresh lockfile generated in an isolated container works.
- broken: 1259 packages, 43 with `../../../node_modules/.pnpm/...`
- fresh:  1321 packages, all `node_modules/...` paths

This commit regenerates every integration's lockfile inside an
isolated `node:22-slim` container via `npm install
--package-lock-only --legacy-peer-deps` and verifies with `npm ci`.

Author: AlemTuzlak

showcase/integrations/ag2/Dockerfile

@@ -2,9 +2,7 @@
 # Cache bust: 2026-04-07 smoke route
 FROM node:22-slim AS frontend
 WORKDIR /app
-COPY package.json ./
-COPY package-lock.json ./
-RUN ls -la /app/ && echo "--lockfile head--" && head -2 /app/package-lock.json
+COPY package.json package-lock.json ./
 RUN npm ci --legacy-peer-deps
 COPY . .
 RUN npm run build