Standalone function, not gi-private: default mode prompts once for all
tracked-but-ignored files and offers git rm --cached, remembering a
decline per-path in the repo's local git config (gitignore-scrub.skip)
so the same file isn't re-asked. -w/--warn is read-only (prints Warning
lines, no prompt, no mutation) for non-interactive callers like a git
hook. Skips silently above $GITIGNORE_SCRUB_LIMIT tracked files (default
5000) to avoid latency on huge repos.
gi now calls gitignore-scrub at the end of any run that touched
.gitignore.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>