feat(09-03): add RouteToUser types and resolver registry

- Add RouteToUser, ResolvedRecipient, NotifyResolver, UserRouteFallback,
  UserRouteFallbackReason types to lib/types/pipeline.ts (ROUTE-01)
- Create lib/services/pipeline-steps/notify-resolvers.ts with three v1
  resolvers: direct_email, pulse_user_id, autotask_resource_email (ROUTE-02)
- Resolver registry as Map<string, NotifyResolver> with registerResolver()
  and resolveRecipient() dispatcher with try/catch error handling

lib/types/pipeline.ts

@@ -192,3 +192,55 @@ export interface UserEventSubscription {
   enabled: boolean;
   updated_at: Date;
 }
+
+// ============================================================================
+// Phase 9 — notify step per-user routing (ROUTE-01..06)
+// ============================================================================
+
+/** Resolver name; resolvers live in lib/services/pipeline-steps/notify-resolvers.ts. */
+export type ResolverName = 'autotask_resource_email' | 'direct_email' | 'pulse_user_id' | string;
+
+/** Optional block on a `notify` step's config. When present, the step attempts
+ *  delivery via the resolved Pulse user's personal channel before falling back
+ *  to the step's `channel_id`.
+ *
+ *  v1 limitation: `field` is a single-level key; dotted paths like 'company.id'
+ *  are NOT walked. Admins must surface needed values at top level of the source
+ *  object (e.g., via an upstream transform step). */
+export interface RouteToUser {
+  /** PipelineContext key whose value holds the entity (e.g. 'ticket'). */
+  source: string;
+  /** Single-level field name within context[source] (e.g. 'assignedResourceID').
+   *  v1 only: single-level lookup — dotted paths like 'company.id' are NOT walked. */
+  field: string;
+  /** Resolver name. Looks up the user from the field value. */
+  resolve: ResolverName;
+  /** Event key checked against user_event_subscriptions for muting (D-12). */
+  event_key: string;
+  /** Optional preferred channel type (D-10). When omitted: ntfy then teams then fallback. */
+  channel_type?: 'teams' | 'ntfy';
+}
+
+/** Output of a resolver. null = no recipient (notify.ts falls through to global). */
+export type ResolvedRecipient =
+  | { user_id: string }
+  | { email: string }
+  | null;
+
+/** A resolver fn. Pure async; reads from postgres if it needs to. */
+export type NotifyResolver = (fieldValue: unknown) => Promise<ResolvedRecipient>;
+
+/** Reasons recorded in execution_step.output_data when fallback occurs (D-11). */
+export type UserRouteFallbackReason =
+  | 'no_channel'
+  | 'send_failed'
+  | 'user_not_found'
+  | 'no_field_value'
+  | 'resolver_unknown';
+
+export interface UserRouteFallback {
+  reason: UserRouteFallbackReason;
+  user_id?: string;
+  channel_type: string;
+  error?: string;
+}