feat(shared): add core domain types

Pod/Engineer, EngineerContext (live pre-push signal), Collision, and
Intervention — the type contract between frontend and backend.

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

shared/src/intervention.ts

@@ -0,0 +1,24 @@
+export type InterventionKind = 'voice' | 'card';
+
+export type InterventionStatus = 'pending' | 'delivered' | 'accepted' | 'dismissed';
+
+export type SuggestedActionKind = 'open_sync_pr' | 'ping_teammate' | 'none';
+
+/** What PodMan says/does about a collision — the product's hero output. */
+export interface Intervention {
+  id: string;
+  collisionId: string;
+  podId: string;
+  kind: InterventionKind;
+  /** Spoken/displayed message, e.g. "Karti and Yahya are both in auth.ts...". */
+  message: string;
+  suggestedAction: SuggestedAction;
+  status: InterventionStatus;
+  createdAt: string;
+}
+
+export interface SuggestedAction {
+  kind: SuggestedActionKind;
+  /** Free-form payload for the action (e.g. branch names for a sync PR). */
+  params?: Record<string, unknown>;
+}