chore(librarian): use frozen lockfile and workspace for generator build

[bshaffer]

Use pnpm install --frozen-lockfile --ignore-scripts in librarian.yaml once the next gapic-generator tag is released after #9381.

[gemini-code-assist]

Code Review

This pull request updates the build step in librarian.yaml to use pnpm install with --frozen-lockfile and --ignore-scripts. The reviewer notes that the package URL and checksum still point to the older v5.3.0 release and suggests verifying if a newer version is required for this command.

[gemini-code-assist]

The pull request description indicates that pnpm install --frozen-lockfile --ignore-scripts should be used once the next gapic-generator tag is released. However, the package URL (line 25) and checksum (line 26) are still pointing to the older v5.3.0 release. Before flagging this version as invalid or outdated, please verify the version against other active repositories in the organization (e.g., google-cloud-go) to ensure consistency. If a newer version is indeed active and required for this command, please update the package version and checksum accordingly.

References

1. When validating tool versions (such as protoc) in configuration files like librarian.yaml, verify the version against other active repositories in the organization (e.g., google-cloud-go) before flagging it as invalid.