chore: move to pnpm

[geromegrignon]

Description

Related issues

Fixes #

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that changes the public API)
• Documentation only
• Refactor, test, or chore (no user-facing change)

Breaking changes

None

Test plan

• npm run build
• npm test
• npm run lint
• Verified in the demo app (if applicable)

Checklist

• Issue discussed or bug clearly described (link issue when applicable)
• Tests added or updated for behavioral changes
• Documentation updated (README, JSDoc, migration notes as needed)
• Public API changes documented; breaking changes called out
• CHANGELOG updated (if the repository maintains one and the change is user-facing)
• Commit messages follow Conventional Commits
• I agree to follow the OpenNG Foundation Code of Conduct

Additional context

[Copilot]

Pull request overview

This PR starts migrating the repo from npm to pnpm by pinning pnpm via packageManager, updating root scripts to invoke pnpm, and adding pnpm workspace configuration for native build allowlisting.

Changes:

• Add packageManager: pnpm@11.18.0 and switch test/build-related scripts to pnpm.
• Add pnpm-workspace.yaml with build-script allowlisting for select native dependencies.
• Ignore pnpm-debug.log in .gitignore.

Reviewed changes

Copilot reviewed 2 out of 5 changed files in this pull request and generated 2 comments.

File	Description
pnpm-workspace.yaml	Introduces pnpm workspace-related configuration (currently only build allowlisting).
package.json	Pins pnpm and updates scripts to call pnpm for library tests and post-build steps.
.gitignore	Adds pnpm debug log to ignored files.

Suppressed comments (1)

package.json:17

• postbuild:lib currently calls pnpm .... Since the CI workflow runs npm run build:lib, npm will also run the postbuild:lib lifecycle script, and this will fail if pnpm is not installed. Wrapping with corepack pnpm keeps it working under both npm run and pnpm run.

    "postbuild:lib": "cp README.md dist/openng/cashew && pnpm run build:schematics",

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[dominicbachmann]

nice!