- Gate cached nu_scripts completion modules on per-version validity
markers so an outdated completion file no longer aborts the whole
config load; incompatible files automatically fall back to noop.
- Add 'pj completion doctor' to report enabled/disabled completions.
- Detect macOS via 'macos'/'mac'/'darwin' so the prompt shows the Apple
icon instead of the Unknown symbol.
- only clone missing nu_scripts cache when using -u/-f
- keep default pj completion as non-cloning check mode
- align completion flag help text with new behavior
- generate cache registry module from command list and load it at startup
- add pj completion sync (-s) with optional help and restart behavior
- keep missing-cache fallback via noop module and preserve cache ignore rules
- switch completion module imports to export use so externs propagate
- extend managed completion command set and required file checks
- rename prompt static cache env var to PJ_LEFT_PROMPT_STATIC_PART
- load completion module via use in nu_polyjuice