ci: make release publishing work on `release` events (#111)

`sbt ci-release` decides between a stable release and a snapshot by
inspecting the ref (`GITHUB_REF` / `CI_COMMIT_TAG`). On `release` events
`GITHUB_REF` can come through empty (as it did for the v2.0.0 release),
so `isTag` was false while the dynver version was a clean `2.0.0` (not a
`-SNAPSHOT`). sbt-ci-release then logged "Snapshot releases must have
-SNAPSHOT version number, doing nothing" and exited 0 — a green job that
published nothing.

Fix:
- pass the release tag explicitly via `CI_COMMIT_TAG`, which sbt-ci-release
  checks before falling back to the (empty) `GITHUB_REF`, forcing the
  stable-release path. Branch pushes leave it empty -> snapshot, as before.
- check out the tag explicitly so dynver computes the right version even
  when the ref is missing.
- add a `workflow_dispatch` (optional `tag` input) to re-run a publish
  manually without cutting a new release.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Cross-build the plugin for sbt 2.x (via sbt2-compat) (#109)

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Ondra Pelech <ondra.pelech@gmail.com>

sbt versionScheme (#105)

Support resolving images from local Docker daemon (with `docker://` p…

…refix) (#102)

Revert "issue-96: adding volume and working directory support (#97)" (#…

…101)

This reverts commit e9ccee5.

support specify permissions to extraMapping (#98)

issue-96: adding volume and working directory support (#97)

Bump jib-core (#93)

Fix release (#92)

Update README.md (#80)

Co-authored-by: Ondra Pelech <ondra.pelech@gmail.com>