build(pnpm): require reviewed dependency build scripts (#17558)

## Description

Enable pnpm's reviewed build-script gate for this repo.

## What changed

- added `strictDepBuilds: true` to `pnpm-workspace.yaml`

## Why

The repo already uses pinned pnpm and frozen installs in CI. This adds
the remaining guard so dependency build scripts do not run unless they
are explicitly reviewed.

## Validation

- ran `pnpm install --frozen-lockfile`

Co-authored-by: Codex <noreply@openai.com>

pnpm-workspace.yaml

@@ -9,3 +9,4 @@ ignoredBuiltDependencies:
 minimumReleaseAge: 10080
 
 blockExoticSubdeps: true
+strictDepBuilds: true