feat: add DBOS skills for TypeScript, Python, and Go (#94)

Add three DBOS SDK skills with reference documentation for building
reliable, fault-tolerant applications with durable workflows.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

skills/dbos-golang/references/comm-messages.md

@@ -0,0 +1,57 @@
+---
+title: Use Messages for Workflow Notifications
+impact: MEDIUM
+impactDescription: Enables reliable inter-workflow and external-to-workflow communication
+tags: communication, messages, send, recv, notification
+---
+
+## Use Messages for Workflow Notifications
+
+Use `dbos.Send` to send messages to a workflow and `dbos.Recv` to receive them. Messages are queued per topic and persisted for reliable delivery.
+
+**Incorrect (using external messaging for workflow communication):**
+
+```go
+// External message queue is not integrated with workflow recovery
+ch := make(chan string) // Not durable!
+```
+
+**Correct (using DBOS messages):**
+
+```go
+func checkoutWorkflow(ctx dbos.DBOSContext, orderID string) (string, error) {
+	// Wait for payment notification (timeout 120 seconds)
+	notification, err := dbos.Recv[string](ctx, "payment_status", 120*time.Second)
+	if err != nil {
+		return "", err
+	}
+
+	if notification == "paid" {
+		_, err = dbos.RunAsStep(ctx, func(ctx context.Context) (string, error) {
+			return fulfillOrder(orderID)
+		}, dbos.WithStepName("fulfillOrder"))
+		return "fulfilled", err
+	}
+	_, err = dbos.RunAsStep(ctx, func(ctx context.Context) (string, error) {
+		return cancelOrder(orderID)
+	}, dbos.WithStepName("cancelOrder"))
+	return "cancelled", err
+}
+
+// Send a message from a webhook handler
+func paymentWebhook(ctx dbos.DBOSContext, workflowID, status string) error {
+	return dbos.Send(ctx, workflowID, status, "payment_status")
+}
+```
+
+Key behaviors:
+- `Recv` waits for and consumes the next message for the specified topic
+- Returns the zero value if the wait times out, with a `DBOSError` with code `TimeoutError`
+- Messages without a topic can only be received by `Recv` without a topic
+- Messages are queued per-topic (FIFO)
+
+**Reliability guarantees:**
+- All messages are persisted to the database
+- Messages sent from workflows are delivered exactly-once
+
+Reference: [Workflow Messaging and Notifications](https://docs.dbos.dev/golang/tutorials/workflow-communication#workflow-messaging-and-notifications)