fix: remove 68 tracked files that are also in .gitignore

These files (build artifacts, db files, planning docs) were committed
before their .gitignore rules existed. release-plz detects this as
uncommitted changes and refuses to run.

Files removed from tracking (kept on disk):
- docs/superpowers/{plans,specs}/*.md (caught by docs/** rule)
- tests/ag-ui-app/*/dist/ (caught by nested .gitignore)
- tests/ag-ui-app/*/data/*.db* (caught by nested .gitignore)
- tests/ag-ui-app/frontend/todos.json (caught by nested .gitignore)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 2 people