Moves the root, leaf and bridge modules from v0.15.0 to v0.16.0, which completes draft-fossil-horizon-00 as zit 0.7.1 released it: named horizons with depth, origin seed refusal, and seed binding with its own seed-signing setting. It also adds fossil-compatible check-in signing and TinyGo builds, and fixes clones of an origin holding a dangling delta and a delta cycle that held the write lock. None of the changed APIs (seed.Mint, clearsign.Key.Verify, seed signing settings) are used here, so no code changes are needed. check-in: 2b313403c6 user: 41898282+github-actions[bot]@users.noreply.github.com tags: main, trunk