v1.2.1

fix(ci): use hasChangesets output instead of filesystem check

The previous approach (checking for .changeset/*.md files) was unreliable
because new changesets may land on main after the Release PR is created.
When the Release PR is merged, these new changeset files persist, causing
the detection script to incorrectly report "versioning PR created, not
published" even when npm publish succeeded.

Use changesets/action's `hasChangesets` output instead — it reliably
indicates whether the action created a PR or attempted to publish.

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