feat(workflows): M5 — SDK workflow::start + admin run API + pic CLI

The user-facing surface for the durable DAG engine. A workflow run can now be
started three ways, all resolving the workflow by name in the caller's app
(`cx.app_id` / the resolved app — never a passed-in arg, the isolation
boundary), seeding a run the orchestrator advances.

SDK seam (shared):
- `WorkflowService` trait + `NoopWorkflowService` + `WorkflowError` in
  `shared::workflow` (mirrors `InvokeService`); added to `Services` as a
  noop-defaulted `with_workflow` builder (all `Services::new` call sites
  unchanged).
- `WorkflowServiceImpl` (manager-core): resolves + seeds a run; authenticated
  callers gated on `AppInvoke` (anonymous skips, script-as-gate), the same gate
  `invoke()` uses.
- `executor-core::sdk::workflow` — the Rhai bridge `workflow::start(name, input)`
  / `workflow::start(name)`, registered in `register_all`. Returns the run id.

Admin API (manager-core `workflows_api`, mounted in the binary):
- `GET  /apps/{app}/workflows`              — definitions (AppRead)
- `POST /apps/{app}/workflows/{name}/runs`  — start a run (AppInvoke)
- `GET  /apps/{app}/workflows/{name}/runs`  — run history (AppRead)
- `GET  /apps/{app}/workflow-runs/{run_id}` — one run + its steps (AppRead)
  `app_id` scopes every query; a foreign run 404s.

CLI (`pic workflows`): `ls` · `run <name> [--input JSON]` · `runs <name>` ·
`run-status <run_id>` — all `--app`-scoped; run definitions stay declarative
(`[[workflows]]` → `pic apply`).

Also: `list_runs_for_workflow` repo reader.

Tests: `workflow_service_start_seeds_a_run` (DB-gated — the SDK/API-shared
entry) + `workflow_run_executes_end_to_end` CLI journey (apply → `pic workflows
run` → poll `run-status` → succeeded, through the real binary + orchestrator).
fmt + clippy -D warnings clean, 449 manager-core lib tests, 14 orchestrator DB
tests, 18 executor-core lib tests, 3 workflow CLI journeys green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/shared/src/services.rs

@@ -26,8 +26,9 @@ use crate::{
     NoopEmailService, NoopEventEmitter, NoopFilesService, NoopGroupDocsService,
     NoopGroupFilesService, NoopGroupKvService, NoopGroupPubsubService, NoopGroupQueueService,
     NoopHttpService, NoopInvokeService, NoopKvService, NoopModuleSource, NoopPubsubService,
-    NoopQueueService, NoopSecretsService, NoopUsersService, NoopVarsService, PubsubService,
-    QueueService, SecretsService, ServiceEventEmitter, UsersService, VarsService,
+    NoopQueueService, NoopSecretsService, NoopUsersService, NoopVarsService, NoopWorkflowService,
+    PubsubService, QueueService, SecretsService, ServiceEventEmitter, UsersService, VarsService,
+    WorkflowService,
 };
 
 /// SDK service bundle. See module docs for the lifecycle and the v1.1.x
@@ -146,6 +147,11 @@ pub struct Services {
     /// drained by competing per-descendant consumers. Wired via
     /// [`Services::with_group_queue`]; defaults to `NoopGroupQueueService`.
     pub group_queue: Arc<dyn GroupQueueService>,
+
+    /// v1.2 Workflows (M5). Scripts get `workflow::start(name, input)` — start a
+    /// run of a named workflow in the caller's app. Wired via
+    /// [`Services::with_workflow`]; defaults to `NoopWorkflowService`.
+    pub workflow: Arc<dyn WorkflowService>,
 }
 
 impl Services {
@@ -193,9 +199,18 @@ impl Services {
             group_files: Arc::new(NoopGroupFilesService),
             group_pubsub: Arc::new(NoopGroupPubsubService),
             group_queue: Arc::new(NoopGroupQueueService),
+            workflow: Arc::new(NoopWorkflowService),
         }
     }
 
+    /// Set the v1.2 Workflows service (picloud binary wires the Postgres-backed
+    /// impl; tests leave the noop default).
+    #[must_use]
+    pub fn with_workflow(mut self, workflow: Arc<dyn WorkflowService>) -> Self {
+        self.workflow = workflow;
+        self
+    }
+
     /// Set the §11.6 shared group-KV service (the picloud binary wires the
     /// Postgres-backed impl; tests leave the noop default).
     #[must_use]