chore: add Amp orb setup script

Installs the pinned pnpm, dependencies, and runs dev:prepare so fresh orbs start ready.

Amp-Thread-ID: https://ampcode.com/threads/T-01a1686c-0d01-731b-9da7-773ec68f49ed
Co-authored-by: Amp <amp@ampcode.com>

Author: Sebastien Chopin

.agents/setup

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+# Prepares an Amp orb for this repository: pinned pnpm, dependencies, and stubbed module build.
+set -euo pipefail
+
+cd "$(dirname "${BASH_SOURCE[0]}")/.."
+
+step() {
+  local name="$1"
+  shift
+  echo "==> $name"
+  local start=$SECONDS
+  "$@"
+  echo "<== $name ($((SECONDS - start))s)"
+}
+
+ensure_pnpm() {
+  local wanted
+  wanted="$(node -p "require('./package.json').packageManager.split('@')[1]")"
+  if [[ "$(pnpm --version 2>/dev/null || true)" != "$wanted" ]]; then
+    npm install --global --no-fund --no-audit "pnpm@$wanted"
+  fi
+  pnpm --version
+}
+
+step "pnpm" ensure_pnpm
+step "pnpm install" pnpm install --frozen-lockfile --prefer-offline
+step "dev:prepare" pnpm run dev:prepare

.gitignore

@@ -53,3 +53,6 @@ Temporary Items
 
 .data
 playgrounds/nuxt/.data
+
+# Amp
+.amp/portals/*