docs: adopt standing development standards #5

	name: Enforce main->develop linear sync policy

	on:
	pull_request:
	types: [opened, edited, synchronize, reopened]
	branches: [develop]

	permissions:
	contents: read

	jobs:
	enforce-sync-policy:
	runs-on: ubuntu-latest
	steps:
	- name: Block direct main->develop PRs
	if: github.event.pull_request.head.ref == 'main'
	run: \|
	echo "Direct main->develop PRs are blocked by linear sync governance." >&2
	echo "Use a develop-based sync branch and cherry-pick selected main commits." >&2
	echo "Runbook: docs/development/main-develop-sync-runbook.md" >&2
	exit 1

	- name: Checkout PR head for merge-commit policy check
	uses: actions/checkout@v4
	with:
	fetch-depth: 0
	ref: ${{ github.event.pull_request.head.sha }}

	- name: Ensure sync branch is linear (no merge commits)
	run: \|
	set -euo pipefail
	git fetch origin "${{ github.base_ref }}" --depth=1
	merges="$(git rev-list --merges "origin/${{ github.base_ref }}..HEAD" \| wc -l \| tr -d ' ')"
	if [ "$merges" != "0" ]; then
	echo "PR branch contains merge commits ($merges). Linear sync policy requires a merge-free branch." >&2
	exit 1
	fi
	echo "Linear sync policy check passed."

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