Support PACKAGE@VERSION tag format

[dionysuzx]

Summary

• Accept PACKAGE@VERSION and PACKAGE@vVERSION as singular announcement tags, alongside PACKAGE-VERSION and PACKAGE/VERSION.

Why

• @ is a common, unambiguous separator (e.g., npm uses it).
• Improves readability with hyphenated names (foo-bar@1.2.3).
• GitHub tag filters already match semver; only parsing blocks this.

Examples

• foo@1.2.3 → singular for “foo”
• bar@v0.9.0 → singular for “bar”

Proposal

• Extend axotag parsing to treat @ as a valid separator before the version (strip optional leading v, then parse semver).
• Update docs to list PACKAGE@VERSION as supported.

NOTE: This issue was created with an LLM but reviewed by dionysuzx.