feat(shared): SdkCallCx, Services bundle, ServiceEventEmitter trait shape

Foundation for the v1.1.x stateful SDK services. Lands the shape only:

  - SdkCallCx — per-call context plumbed into every future service
    trait method (app_id, principal, execution/request ids, trigger
    depth slots).
  - Services — empty non_exhaustive bundle; v1.1.1 (KV) adds the first
    field, subsequent PRs follow.
  - ServiceEventEmitter — async trait future services emit through;
    real outbox-backed impl lands with triggers in v1.1.1. NoopEventEmitter
    is the v1.1.0 default.

No behaviour change. Subsequent commits in this PR plumb these types
through executor-core and the orchestrator dispatch path.

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

crates/shared/src/sdk_cx.rs

@@ -0,0 +1,54 @@
+//! `SdkCallCx` — per-call context every stateful SDK service receives.
+//!
+//! Service trait methods (added by subsequent v1.1.x PRs starting with
+//! KV) all take `&SdkCallCx` so they can:
+//!   * scope by `app_id` for cross-app isolation,
+//!   * audit `principal` when authenticated,
+//!   * carry `execution_id` / `request_id` into emitted events,
+//!   * bound trigger chains via `trigger_depth` / `root_execution_id`.
+//!
+//! The struct lives in `picloud-shared` (not `executor-core`) because
+//! future service impls live in `manager-core` and the trait that hands
+//! the cx in is shared by both sides. Pure value type — no handles, no
+//! DB pool references, no allocations beyond what's in `Principal`.
+
+use crate::{AppId, ExecutionId, Principal, RequestId};
+
+/// Per-invocation context for every stateful SDK service call.
+///
+/// Constructed once at the start of an invocation by `executor-core`
+/// from the incoming `ExecRequest`, then handed (by reference) to every
+/// service trait method the script triggers during execution. Services
+/// MUST derive `app_id` from this struct — never from script-passed
+/// arguments — to preserve cross-app isolation.
+#[derive(Debug, Clone)]
+pub struct SdkCallCx {
+    /// Owning application for this invocation. Source of truth for
+    /// every `(app_id, …)` storage lookup the script makes.
+    pub app_id: AppId,
+
+    /// Caller identity, when authenticated. `None` for unauthenticated
+    /// data-plane HTTP requests (the common case for public endpoints);
+    /// `Some` when the call came in via the dashboard, an API key, or a
+    /// future authed surface.
+    pub principal: Option<Principal>,
+
+    /// Unique id for THIS execution. Matches `ExecRequest.execution_id`.
+    pub execution_id: ExecutionId,
+
+    /// Unique id for the ingress request that started the chain. The
+    /// same `request_id` is shared across every execution triggered by
+    /// the same request (direct + trigger fan-out).
+    pub request_id: RequestId,
+
+    /// `0` for direct invocations (HTTP request, manual run). Each
+    /// indirect invocation through the triggers framework (v1.1.1)
+    /// increments this; the dispatcher rejects beyond a configured
+    /// ceiling to prevent runaway feedback loops.
+    pub trigger_depth: u32,
+
+    /// `== execution_id` when `trigger_depth == 0`; otherwise the
+    /// `execution_id` of the original ingress execution. Lets the audit
+    /// log group every fan-out execution under the originating event.
+    pub root_execution_id: ExecutionId,
+}