v0.2.3 — DX fix for git+https install

Bridge-ui flagged that npm install git+https://...#v0.2.2 doesn't
work for fresh consumers — pnpm/npm/yarn pull source but don't run
build, and our `files` allowlist ships dist/ only. Adding
"prepare": "tsup" to package.json scripts runs the build
automatically after install from git sources, so dist/ is
materialized in-place.

No wire change, no source change. 550/550 tests still pass.

Install:
  npm install git+https://gitlab.syncad.com/hive/velocity-js-sdk.git#v0.2.3

This tag is also the first cut targeted for npm public publish.