chore: demote breaking changes to minor while pre-v1

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: FBumann

.release-please-config.json

@@ -5,6 +5,7 @@
     ".": {
       "release-type": "simple",
       "package-name": "fluxopt-plot",
+      "bump-minor-for-major-pre-major": true,
       "bump-patch-for-minor-pre-major": true,
       "changelog-path": "CHANGELOG.md",
       "prerelease": true,