Sync retry/backoff npm install logic to setup-api-client template

[Copilot]

The template copy of setup-api-client at templates/consumer-repo/.github/actions/setup-api-client/action.yml was missing the exponential-backoff retry loop and pinned lru-cache@10.4.3 added to the main action in #1656, causing template drift.

Changes

• templates/consumer-repo/.github/actions/setup-api-client/action.yml
  • Replace single-attempt install (with one --legacy-peer-deps fallback) with a 3-attempt loop using exponential backoff (5s → 10s → 20s)
  • Pin lru-cache@10.4.3 (was lru-cache@^10.0.0)
  • Apply --legacy-peer-deps fallback on first failure before sleeping and retrying
  • Fail explicitly with ::error:: after all attempts exhausted

The template now matches the main action exactly:

NPM_MAX_RETRIES=3
NPM_BACKOFF=5  # doubles each retry (5, 10, 20)
npm_installed=false

for (( attempt=1; attempt<=NPM_MAX_RETRIES; attempt++ )); do
  if npm install --no-save --location=project "${NPM_PACKAGES[@]}"; then
    npm_installed=true; break
  fi
  # attempt 1: also retry with --legacy-peer-deps
  # subsequent: sleep with backoff
done

if [ "$npm_installed" != "true" ]; then
  echo "::error::npm install failed after $NPM_MAX_RETRIES attempts"
  exit 1
fi

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