ci: make sure -dev version suffix is not forgotten after release

Workflow checks that PRs are made only when current version ends with -dev
If this fails, a commit bumping the version to -dev should be pushed to main branch.

.github/workflows/dev-version.yml

@@ -0,0 +1,23 @@
+# Check that PRs are made against the -dev version.
+# 
+# If this fails, push commit to update the version to -dev to main.
+
+name: Check for -dev version
+
+on:
+  pull_request:
+
+permissions: {}
+
+jobs:
+  check_dev_version:
+    name: Check that current version ends with -dev
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          show-progress: false
+          persist-credentials: false
+
+      - name: Run version-checking script
+        run: scripts/check-dev-version.py

scripts/check-dev-version.py

@@ -0,0 +1,23 @@
+#!/usr/bin/env python3
+#
+# Script to check that current version ends with -dev.
+# Meant to be run in CI to check that PRs are made against the -dev version.
+# If the version is not -dev, it was forgotten to be updated
+# after making a release.
+
+from pathlib import Path
+import tomllib
+import sys
+
+
+def main():
+    with Path("Cargo.toml").open("rb") as fp:
+        cargo_toml = tomllib.load(fp)
+    version = cargo_toml["package"]["version"]
+    if not version.endswith("-dev"):
+        print(f"Current version {version} does not end with -dev", file=sys.stderr)
+        sys.exit(1)
+
+
+if __name__ == "__main__":
+    main()