v0.2.0 — Zod types, layered subpaths, full role coverage

Re-platformed onto Rust-sourced Zod schemas (single source of truth, runtime-validated), 11 per-role subpath exports, full plugin-role coverage, PROTOCOL_VERSION 1.1.0, subject/delete, and provider run/cancel concurrency. Back-compat preserved for existing subject/trigger plugins. 64 tests.