<!-- auto-generated by pr-learnings -->

## buildNode.groovy: pnpm must be globally installed before invoking pnpm commands

**Takeaway:** When auto-selecting the install command in `buildNode.groovy` based on lockfile presence, pnpm must be installed globally first (`npm install -g pnpm@<version>`) — emitting `pnpm install --frozen-lockfile` alone will fail in environments where pnpm is not on the PATH.

**Pattern:** Any time `buildNode.groovy` detects a `pnpm-lock.yaml` and constructs an `npm_install_arg` that invokes `pnpm`, the command string must prefix with a global install step. The version should be pinned to avoid silent drift.

**Rationale:** Jenkins agents running Node builds do not have pnpm pre-installed. The auto-selection logic that branches on `fileExists("${repo_name}/pnpm-lock.yaml")` is responsible for producing a self-contained, executable command string — if pnpm is absent from the agent PATH the build fails with a command-not-found error. Reviewers also flagged that lock-file cleanup helpers should cover `pnpm-lock.yaml` alongside `package-lock.json`.

**Concrete example** (from [PR #727](https://github.com/Meesho/devops-lib/pull/727), `src/com/meesho/stages/buildNode.groovy:L193`):

```groovy
// Before (incomplete — pnpm not guaranteed on PATH)
if (fileExists("${repo_name}/pnpm-lock.yaml")) {
    npm_install_arg = 'pnpm install --frozen-lockfile'
}

// After (reviewer-suggested correction)
if (fileExists("${repo_name}/pnpm-lock.yaml")) {
    npm_install_arg = 'npm install -g pnpm@10.33.0 && pnpm install --frozen-lockfile'
}
```

**Examples from PRs:**
- [PR #727](https://github.com/Meesho/devops-lib/pull/727): Auto-selection logic added for pnpm/npm-ci/npm-install; reviewer caught that pnpm must be globally installed first.
- [PR #728](https://github.com/Meesho/devops-lib/pull/728): Reviewer noted cleanup helpers should also handle `pnpm-lock.yaml`.