fix(ci): make mark-stable main-only and cancel stale runs

scripts/github/mark-stable-if-highest-version.sh

@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+git config user.name "github-actions[bot]"
+git config user.email "github-actions[bot]@users.noreply.github.com"
+
+echo "Ref: $GITHUB_REF"
+echo "SHA: $GITHUB_SHA"
+
+VERSION="${GITHUB_REF#refs/tags/}"
+echo "Current version tag: ${VERSION}"
+
+echo "Collecting all version tags..."
+ALL_V_TAGS="$(git tag --list 'v*' || true)"
+
+if [[ -z "${ALL_V_TAGS}" ]]; then
+  echo "No version tags found. Skipping stable update."
+  exit 0
+fi
+
+echo "All version tags:"
+echo "${ALL_V_TAGS}"
+
+LATEST_TAG="$(printf '%s\n' "${ALL_V_TAGS}" | sort -V | tail -n1)"
+
+echo "Highest version tag: ${LATEST_TAG}"
+
+if [[ "${VERSION}" != "${LATEST_TAG}" ]]; then
+  echo "Current version ${VERSION} is NOT the highest version."
+  echo "Stable tag will NOT be updated."
+  exit 0
+fi
+
+echo "Current version ${VERSION} IS the highest version."
+echo "Updating 'stable' tag..."
+
+git tag -d stable 2>/dev/null || true
+git push origin :refs/tags/stable || true
+
+git tag stable "$GITHUB_SHA"
+git push origin stable
+
+echo "Stable tag updated to ${VERSION}."