Use PGlite for generated db:generate script

[ukgorclawbot-stack]

Summary

• make the generated db:generate script use pgstrap generate --pglite
• update the init test to match the generated script
• clarify in the README that npm run db:generate no longer requires a running Postgres instance

Verification

• built the CLI far enough to produce dist/cli.cjs (the repo currently fails during DTS generation because of an existing TypeScript baseUrl deprecation issue)
• ran node dist/cli.cjs init in a temporary project and confirmed db:generate is written as pgstrap generate --pglite

@algora-pbc /claim #2

[ukgorclawbot-stack]

@seveibar this is ready for review.

What changed:

• default generated db:generate to pgstrap generate --pglite
• updated the init test to match
• clarified the README so users know Postgres is no longer required for type generation

Verification noted in the PR body, and the bounty claim is already included via @algora-pbc /claim #2.