fix(semver): skip non-semver tags when picking latest existing tag

Rolling tags like 'v1' (and any other tag that doesn't parse as x.y.z
after prefix stripping) used to enter the latest-tag candidate set in
CalculateSemver. When such a tag shared a commit with a real semver tag
(e.g. v1 and v1.16.3 both pointing at the same release commit), go-git's
alphabetical tag iteration made 'v1' win, ParseExistingSemver bailed out
because '1' has only one component, and the calculator silently reset
the baseline to 0.0.0 — producing nonsense like 0.0.5 on this branch.

ListExistingTags now filters tags through a new IsParseableSemverTag
helper before recording them, so non-semver tags never participate in
latest-tag selection. The behavior change is invisible for repos that
only use proper vX.Y.Z tags, and it's covered by a new test table.

cmd/utils/git.go

@@ -163,10 +163,13 @@ func ListCommits(repo *GitRepository) ([]CommitDetails, error) {
 }
 
 // ListExistingTags lists all tags in the repository
-func ListExistingTags(repo *GitRepository) {
+// ListExistingTags lists all tags in the repository.
+// Tags that don't parse as proper semver (rolling tags like "v1" or "latest")
+// are skipped so they can't out-rank real semver tags pointing to the same
+// commit during latest-tag selection.
+func ListExistingTags(repo *GitRepository, tagPrefixes []string) {
 	Debug("Listing existing tags", nil)
 
-	// Check if Handler is nil to avoid panic
 	if repo.Handler == nil {
 		Debug("Repository handler is nil, skipping tag listing", nil)
 		return
@@ -180,15 +183,17 @@ func ListExistingTags(repo *GitRepository) {
 
 	if err := refs.ForEach(func(ref *plumbing.Reference) error {
 		tagName := ref.Name().Short()
-		commitHash := ref.Hash().String()
 
-		// For annotated tags, dereference to get the actual commit hash
+		if !IsParseableSemverTag(tagName, tagPrefixes) {
+			Debug("Skipping non-semver tag", map[string]interface{}{"tag": tagName})
+			return nil
+		}
+
+		commitHash := ref.Hash().String()
 		tagObj, err := repo.Handler.TagObject(ref.Hash())
 		if err == nil {
-			// This is an annotated tag - get the commit it points to
 			commitHash = tagObj.Target.String()
 		}
-		// If err != nil, it's a lightweight tag - ref.Hash() is already the commit hash
 
 		repo.Tags = append(repo.Tags, TagDetails{
 			Name: tagName,