This PR fixes a false positive in `release_checklist.py` where the check
for the dev cycle being started would fail even when it was correctly
set up.
The script was looking for `set(LEAN_VERSION_IS_RELEASE 0)` as an exact
prefix match, but CMakeLists.txt uses the CMake cache variable form:
`set(LEAN_VERSION_IS_RELEASE 0 CACHE STRING "")`. The fix uses a regex
that handles both syntaxes.
This was discovered during the v4.29.0-rc4 release when the checklist
incorrectly reported that a "begin dev cycle" PR was needed, even though
PR #12526 had already set `LEAN_VERSION_IS_RELEASE 0` and
`LEAN_VERSION_MINOR 30` on master.
🤖 Prepared with Claude Code
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>