v1.2.0

Slim CI matrix to ubuntu-only and clean up ruff lint

With no native code, the windows/macos legs caught essentially nothing OS-specific. CI matrix is now ubuntu-latest x Python 3.10-3.14 (5 jobs instead of 15); release job is unchanged.

Ruff autofixes (also clears the lint job in CI): tidy import ordering in the new numpy ports, swap @lru_cache(maxsize=None) for @functools.cache, and drop the unused single-theta SHT kernel imports in sht.py — they were re-exports from _sht for back-compat but no caller uses them.