chore(gitignore): adopt #67/#68 canonical entries, untrack ui/package-lock.json (#11)

Adds the canonical `.gitignore` blocks from rsr-template-repo /
v3-templater and removes `ui/package-lock.json` from tracking
(file remains on disk locally).

Existing tracked `.editorconfig` is left in place per standards#68's
owner ruling that removing tracked copies is a separate per-repo
chore.

Refs hyperpolymath/standards#66
Refs hyperpolymath/standards#67
Refs hyperpolymath/standards#68

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath