Fix CI: prevent better-sqlite3 install, add data dir for migrations
- Add .npmrc with auto-install-peers=false to prevent pnpm from
auto-installing better-sqlite3 as a peer dependency
- Update package.json pnpm config to ignore missing better-sqlite3 peer
- Add gnused to nixpkgs for lex-cli
- Create data directory before running migrations in CI
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>