fix: CI release versioning — use sorted tags instead of git describe

git describe picks an arbitrary tag when multiple tags point to the
same commit (v0.0.4 and v0.0.5 both on 4f1a01e), causing duplicate
release attempts. Switch to `git tag -l --sort=-v:refname` for
reliable highest-version detection. Also add fetch-tags: true.

Author: claude

.github/workflows/ci.yml

@@ -238,12 +238,14 @@ jobs:
         uses: actions/checkout@v4
         with:
           fetch-depth: 0
+          fetch-tags: true
 
       - name: Determine version bump
         id: version
         run: |
-          # Get latest tag or default to v0.0.0
-          LATEST_TAG=$(git describe --tags --abbrev=0 2>/dev/null || echo "v0.0.0")
+          # Get highest semver tag (git describe can pick wrong tag when multiple tags share a commit)
+          LATEST_TAG=$(git tag -l 'v*' --sort=-v:refname | head -1)
+          LATEST_TAG="${LATEST_TAG:-v0.0.0}"
           echo "latest_tag=$LATEST_TAG" >> $GITHUB_OUTPUT
 
           # Parse current version