Adds a new merge commitSha restoration script (`scripts/restore-merge-sha-fn-3878.mjs`) with test coverage to handle a specific FN-3878 merge case, along with a changeset for publishing and a minor plugin vitest config governance alignment across three plugins.
Fusion-Task-Id: FN-3878
- Add a new fusion-plugin-even-cards package with typed card formatting utilities and board/task card generation
- Implement authenticated plugin routes for board card endpoints and plugin registration wiring
- Add unit tests for auth handling, board routes, and card formatting behavior
- Document plugin in PLUGIN_AUTHORING guide and register it in pnpm workspace
Fusion-Task-Id: FN-3739
