Add pi-tasklight CI, package, and release checks

[revazi]

Context

The Tasklight CLI repo now has stronger CI/repo hygiene. pi-tasklight should have its own checks, but they belong in this repository because this package is separate.

Plan

Add or verify:

• formatting/lint checks
• unit tests
• package dry-run / package contents check
• install smoke test where practical
• GitHub Actions with pinned actions
• Dependabot for npm and actions
• release workflow for @tasklight/pi-tasklight

Acceptance criteria

• PR checks cover the package without relying on the Tasklight CLI repo.
• Release workflow validates package version/tag/changelog.
• npm publishing remains controlled/approved.