build: migrate from Lerna to Changesets #1

	name: Changeset

	# Verifies that every PR carries a changeset (or an explicit empty one).
	# Runs only on pull_request — `push` to main carries already-merged
	# changesets that the Release workflow then consumes.

	on:
	pull_request:
	branches: [main]
	workflow_dispatch:
	inputs:
	pr_number:
	description: "PR number to test (for fork PRs)"
	required: true
	type: string

	permissions:
	contents: read

	jobs:
	changeset:
	name: Changeset present
	runs-on: ubuntu-latest
	# Skip on the auto-generated "Version Packages" PR (it consumes all changesets).
	if: github.head_ref != 'changeset-release/main'
	steps:
	- uses: actions/checkout@v4
	with:
	ref: ${{ inputs.pr_number && format('refs/pull/{0}/head', inputs.pr_number) \|\| '' }}
	# Full history so `changeset status --since=origin/main` can diff.
	fetch-depth: 0

	- uses: actions/setup-node@v4
	with:
	node-version: 24.x

	- name: Install dependencies
	run: npm ci

	# Fails the PR if no changeset describes the change.
	# Add one with `npm run changeset` (or `npm run changeset:empty` for PRs
	# that don't need a release entry) and commit it.
	# We check `.changesets` (not `.releases`) so that empty changesets
	# — which have 0 package bumps but still document the PR — pass.
	- name: Verify changeset is present
	run: \|
	npx changeset status --since=origin/main --output=/tmp/cs.json
	if [ "$(jq '.changesets \| length' /tmp/cs.json)" -eq 0 ]; then
	echo "::error::No changeset found on this PR. Run 'npm run changeset' (or 'npm run changeset:empty' for PRs that don't need a release entry) and commit the file."
	exit 1
	fi

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