v1.2.1: The local core and event contract v1

Step 2 of milestone 1 (architecture and software).

- Local app: the room now runs on a small local core that serves it on 127.0.0.1 with a per-run token. `codewizards demo` shows simulated wizards with no account and no network.
- Claude Code, experimental: `codewizards serve --repo PATH` drives your own Claude Code. Each task works in its own branch and git worktree, Bash runs inside Claude Code's sandbox, and nothing is committed until you approve the diff on the blackboard.
- Event contract v1: sequence numbers (replaying never doubles anything), the account, model-maker guilds, and events for blocked wizards, quota, failed and cancelled tasks.
- Fixes: the room no longer freezes on an unknown guild, and the v1.1 cleanup finally reached the repository.
- CI: core tests on Linux, macOS and Windows, and a browser smoke test on the packaged app.
- Docs: architecture in docs/arquitectura.md and the step report in auditorias/software.md (in Spanish).

Try the demo: https://poligle.github.io/codewizards/