feat(sandokan-core): B1.1 — contrato del orquestador

Primer crate de la Fase B. Define SOLO el contrato del orquestador
sandokan (library horizontal embebible, no daemon supremo):

- Intent / ExecContext / IsolationLevel — qué orquestar
- ExecHandle — referencia a una entidad encarnada
- LifecycleEvent / TelemetryFrame — observabilidad (wire types)
- EngineError — taxonomía de fallas
- trait Engine — run/stop/list/status/telemetry (poll-based, sin
  streams sobre trait objects, para que las 3 impls lo cumplan
  uniformemente)

Las impls concretas (LocalEngine, DaemonEngine, RemoteEngine) vendrán
en crates separados (sandokan-local, sandokan-daemon, sandokan-remote).

3 tests verdes. cargo check --workspace verde.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

crates/runtime/sandokan-core/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "sandokan-core"
+description = "Contrato del orquestador sandokan: trait Engine + tipos (Intent, ExecHandle, eventos, telemetría). Sin transporte ni impl concreta."
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+authors.workspace = true
+publish.workspace = true
+
+[dependencies]
+brahman-card = { path = "../../protocol/brahman-card" }
+sandokan-lifecycle = { path = "../sandokan-lifecycle" }
+serde = { workspace = true }
+ulid = { workspace = true }
+thiserror = { workspace = true }
+async-trait = { workspace = true }