feat(workflows): M1 — schema + definition validation + declarative reconcile

First milestone of the v1.2 Workflows track (blueprint §9.1/§9.2): the durable
DAG engine's foundation — the definition model, its validation, and the
declarative `apply` reconcile path. No execution yet (the orchestrator is M2).

- Migration 0071_workflows: `workflows` (owner-polymorphic like scripts, app-
  owned in M1), `workflow_runs`, and `workflow_run_steps` (the per-step
  competing-consumer lease table the M2 orchestrator will claim). Schema golden
  reblessed.
- `shared::workflow`: the `WorkflowDefinition` / `WorkflowStepDef` DTOs (shared
  by the CLI, apply, and the future orchestrator) + run/step status enums.
- Pure, DB-free `workflow_template` (input `{{ input.x }}` / `{{ steps.a.output.y }}`
  resolution, type-preserving) and `workflow_expr` (a small safe JSON-predicate
  evaluator for `when` — keeps manager-core free of a scripting engine).
- `workflow_repo`: read trait + reconcile tx free-fns (insert/update/delete).
- apply_service: `BundleWorkflow` + `Plan.workflows` + `CurrentState.workflows`
  + `ApplyReport.workflows_*`; server-side `validate_workflow_definition`
  (unique/acyclic steps via topological sort, deps exist, function XOR workflow,
  `when`/template parse) rejecting on a group node; `diff_workflows` by
  lower(name) (Update on a definition change) + in-tx reconcile.
- CLI: `[[workflows]]` + `[[workflows.steps]]` manifest structs → wire bundle;
  plan/apply render + report counts.
- Tests: 16 manager-core lib tests (template, expr, definition validation) +
  the `workflows` CLI journey (apply → NoOp → prune; cyclic DAG rejected).

Deferred to later milestones: the orchestrator worker (M2), conditional/template
runtime wiring (M3), nested sub-workflows (M4), the SDK/API/CLI run surface
(M5), the dashboard (M6). The `group_id` column + run/step tables ship now so
those slot in without a migration churn.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/shared/src/lib.rs

@@ -46,6 +46,7 @@ pub mod users;
 pub mod validator;
 pub mod vars;
 pub mod version;
+pub mod workflow;
 
 /// serde `default` for `enabled`-style boolean fields that should default to
 /// `true` when absent from the wire (bool's own `Default` is `false`). Shared
@@ -80,7 +81,7 @@ pub use group_queue::{GroupQueueError, GroupQueueService, NoopGroupQueueService}
 pub use http::{HttpError, HttpRequest, HttpResponse, HttpService, NoopHttpService};
 pub use ids::{
     AdminUserId, ApiKeyId, AppId, AppUserId, ExecutionId, GroupId, InvitationId, ProjectId,
-    QueueMessageId, RequestId, ScriptId, TriggerId,
+    QueueMessageId, RequestId, ScriptId, TriggerId, WorkflowId, WorkflowRunId, WorkflowRunStepId,
 };
 pub use inbox::{
     InboxDeliveryOutcome, InboxFailureKind, InboxResolver, InboxResult, NoopInboxResolver,