feat(v1.1.3-modules): top-level script AST cache in LocalExecutorClient

- New `ScriptIdentity { script_id, updated_at }` DTO.
- `ExecutorClient` trait gains an `execute_with_identity` method;
  default impl forwards to `execute` so `RemoteExecutorClient` (and
  cluster-mode transports later) keep working without bespoke caching.
- `LocalExecutorClient` overrides `execute_with_identity` to consult
  an `LruCache<ScriptId, CachedScript>`. Cache hit only when the
  cached entry's `updated_at` matches the caller's identity; mismatch
  triggers a fresh `Engine::compile`. `Engine::execute_ast(&Arc<AST>, req)`
  is called inside `spawn_blocking` exactly as `execute` does today.
- Cache size from `PICLOUD_SCRIPT_CACHE_SIZE` (default 256).
- Orchestrator's HTTP data-plane path and the dispatcher both switch
  to `execute_with_identity`. `ResolvedTrigger` carries
  `script_updated_at` for the dispatcher's identity construction.

Workspace builds; full test suite (~440 tests) green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/orchestrator-core/Cargo.toml

@@ -21,5 +21,10 @@ tracing.workspace = true
 uuid.workspace = true
 chrono.workspace = true
 reqwest.workspace = true
+rhai.workspace = true
 tokio.workspace = true
 urlencoding.workspace = true
+
+# v1.1.3 — top-level script AST cache lives in orchestrator-core's
+# LocalExecutorClient; key is ScriptId, value is `(updated_at, Arc<rhai::AST>)`.
+lru.workspace = true