fix: skip the action self-check until the pinned version is on npm

[MarkAlex1234]

Summary

 action (Action self-check)
+  published?  npm view go-tokenless@<package.json version>
-  uses: ./
+  uses: ./            if published
+  assert status       if published

A release PR bumps the action.yml pin to a version that exists only after the tag is pushed, so the self-check failed with ETARGET on #18.

Evidence

• Before: chore: release 1.1.0 #18 failed with npm error notarget No matching version found for go-tokenless@1.1.0.
• After: the self-check on main passes once 1.1.0 is published. A release PR now gets a notice and skips instead.

Merge danger

Door: two-way.

Blast radius: CI only.