cosmic-crunch 2.1.1

Review-driven fix batch: --year_regex/--date_regex now survive multiprocessing spawn/forkserver (previously silently ignored with --processes > 1 on macOS/Windows), request timeouts on every HTTP call, alternation-safe filter patterns, non-zero exits when convert finds nothing or errors, txt->nc rewrite anchored to exact segments, and support for no-L2 archive layouts. Plus the Read the Docs site shipped in-tag and a README "Use from Python" section with the xarray group read-back.

Full details: CHANGELOG.md