Add shared types package

Shared TypeScript types, Zod validators, API contract definitions,
and constants used by both server and UI. Covers agents, goals,
issues, projects, and activity entities.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/shared/src/validators/goal.ts

@@ -0,0 +1,16 @@
+import { z } from "zod";
+import { GOAL_LEVELS } from "../constants.js";
+
+export const createGoalSchema = z.object({
+  title: z.string().min(1),
+  description: z.string().optional().nullable(),
+  level: z.enum(GOAL_LEVELS),
+  parentId: z.string().uuid().optional().nullable(),
+  ownerId: z.string().uuid().optional().nullable(),
+});
+
+export type CreateGoal = z.infer<typeof createGoalSchema>;
+
+export const updateGoalSchema = createGoalSchema.partial();
+
+export type UpdateGoal = z.infer<typeof updateGoalSchema>;