Add database package with Drizzle schema

Postgres schema via Drizzle ORM for agents, goals, issues, projects,
and activity log tables. Includes migration runner, seed script,
and Drizzle config.

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

packages/db/src/schema/agents.ts

@@ -0,0 +1,15 @@
+import { type AnyPgColumn, pgTable, uuid, text, integer, timestamp, jsonb } from "drizzle-orm/pg-core";
+
+export const agents = pgTable("agents", {
+  id: uuid("id").primaryKey().defaultRandom(),
+  name: text("name").notNull(),
+  role: text("role").notNull().default("general"),
+  status: text("status").notNull().default("idle"),
+  budgetCents: integer("budget_cents").notNull().default(0),
+  spentCents: integer("spent_cents").notNull().default(0),
+  lastHeartbeat: timestamp("last_heartbeat", { withTimezone: true }),
+  reportsTo: uuid("reports_to").references((): AnyPgColumn => agents.id),
+  metadata: jsonb("metadata"),
+  createdAt: timestamp("created_at", { withTimezone: true }).notNull().defaultNow(),
+  updatedAt: timestamp("updated_at", { withTimezone: true }).notNull().defaultNow(),
+});