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/manager-core/tests/workflow_orchestrator.rs

@@ -22,15 +22,17 @@ use picloud_manager_core::workflow_orchestrator::{
     WorkflowOrchestrator, WorkflowOrchestratorConfig,
 };
 use picloud_manager_core::workflow_repo::{
-    claim_ready_step, complete_step_and_advance, get_run, list_run_steps, reclaim_stale_steps,
-    start_run, AdvanceResult, ClaimedStep, NewWorkflowRun, StepOutcome,
+    claim_ready_step, complete_step_and_advance, get_run, list_run_steps, list_runs_for_workflow,
+    reclaim_stale_steps, start_run, AdvanceResult, ClaimedStep, NewWorkflowRun, StepOutcome,
 };
+use picloud_manager_core::workflow_service::WorkflowServiceImpl;
 use picloud_orchestrator_core::{ExecutionGate, ExecutorClient, ScriptIdentity};
 use picloud_shared::workflow::{
     OnError, RunStatus, StepStatus, WorkflowBackoff, WorkflowDefinition, WorkflowRetry,
     WorkflowStepDef,
 };
 use picloud_shared::{AppId, ExecutionLogSink, LogSinkError, WorkflowId};
+use picloud_shared::{RequestId, ScriptId, WorkflowService};
 use serde_json::{json, Value};
 use sqlx::postgres::PgPoolOptions;
 use sqlx::PgPool;
@@ -927,3 +929,59 @@ async fn nesting_depth_ceiling_fails_the_run() {
         "self-nesting run fails at the depth ceiling, not infinitely"
     );
 }
+
+// ===========================================================================
+// M5 — the SDK/API-shared service entry (`WorkflowServiceImpl::start`).
+// ===========================================================================
+
+fn anon_cx(app: AppId) -> picloud_shared::SdkCallCx {
+    let execution_id = picloud_shared::ExecutionId::new();
+    picloud_shared::SdkCallCx {
+        app_id: app,
+        script_id: ScriptId::new(),
+        principal: None,
+        execution_id,
+        request_id: RequestId::new(),
+        trigger_depth: 0,
+        root_execution_id: execution_id,
+        is_dead_letter_handler: false,
+        event: None,
+    }
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn workflow_service_start_seeds_a_run() {
+    let Some(pool) = pool_or_skip().await else {
+        return;
+    };
+    let _claim_guard = lock_and_reset(&pool).await;
+    let app = seed_app(&pool).await;
+    let def = WorkflowDefinition {
+        steps: vec![step("only", "fn_only", &[])],
+    };
+    seed_named_workflow(&pool, app, "svc_wf", &def).await;
+
+    let svc = WorkflowServiceImpl::new(pool.clone());
+    let cx = anon_cx(app);
+
+    // start seeds a durable run with the given input + its steps.
+    let run_id = svc
+        .start(&cx, "svc_wf", json!({ "k": "v" }))
+        .await
+        .expect("start");
+    let r = get_run(&pool, app, run_id).await.unwrap().unwrap();
+    assert_eq!(r.input, json!({ "k": "v" }));
+    let steps = list_run_steps(&pool, run_id).await.unwrap();
+    assert_eq!(steps.len(), 1);
+    assert_eq!(steps[0].step_name, "only");
+    assert_eq!(steps[0].status, StepStatus::Ready); // a root
+
+    // it shows up in the run-history list.
+    let runs = list_runs_for_workflow(&pool, app, r.workflow_id, 10)
+        .await
+        .unwrap();
+    assert_eq!(runs.len(), 1);
+
+    // an unknown workflow name is a not-found error.
+    assert!(svc.start(&cx, "ghost", Value::Null).await.is_err());
+}