feat(04-01): add agents table to database schema

- Define agents table with id, name (unique), taskId, sessionId, worktreeId, status
- Status enum: idle, running, waiting_for_input, stopped, crashed
- Foreign key to tasks with onDelete: 'set null' (agent may outlive task)
- Add agentsRelations linking to tasks
- Export Agent and NewAgent types

src/db/schema.ts

@@ -168,3 +168,32 @@ export const taskDependenciesRelations = relations(taskDependencies, ({ one }) =
 
 export type TaskDependency = InferSelectModel<typeof taskDependencies>;
 export type NewTaskDependency = InferInsertModel<typeof taskDependencies>;
+
+// ============================================================================
+// AGENTS
+// ============================================================================
+
+export const agents = sqliteTable('agents', {
+  id: text('id').primaryKey(),
+  name: text('name').notNull().unique(), // Human-readable name (e.g., 'gastown', 'chinatown')
+  taskId: text('task_id').references(() => tasks.id, { onDelete: 'set null' }), // Task may be deleted
+  sessionId: text('session_id'), // Claude CLI session ID for resumption (null until first run completes)
+  worktreeId: text('worktree_id').notNull(), // WorktreeManager worktree ID
+  status: text('status', {
+    enum: ['idle', 'running', 'waiting_for_input', 'stopped', 'crashed'],
+  })
+    .notNull()
+    .default('idle'),
+  createdAt: integer('created_at', { mode: 'timestamp' }).notNull(),
+  updatedAt: integer('updated_at', { mode: 'timestamp' }).notNull(),
+});
+
+export const agentsRelations = relations(agents, ({ one }) => ({
+  task: one(tasks, {
+    fields: [agents.taskId],
+    references: [tasks.id],
+  }),
+}));
+
+export type Agent = InferSelectModel<typeof agents>;
+export type NewAgent = InferInsertModel<typeof agents>;