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/step-basics.md

@@ -0,0 +1,81 @@
+---
+title: Use Steps for External Operations
+impact: HIGH
+impactDescription: Steps enable recovery by checkpointing results
+tags: step, external, api, checkpoint
+---
+
+## Use Steps for External Operations
+
+Any function that performs complex operations, accesses external APIs, or has side effects should be a step. Step results are checkpointed, enabling workflow recovery.
+
+**Incorrect (external call in workflow):**
+
+```go
+func myWorkflow(ctx dbos.DBOSContext, input string) (string, error) {
+	// External API call directly in workflow - not checkpointed!
+	resp, err := http.Get("https://api.example.com/data")
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+	body, _ := io.ReadAll(resp.Body)
+	return string(body), nil
+}
+```
+
+**Correct (external call in step using `dbos.RunAsStep`):**
+
+```go
+func fetchData(ctx context.Context) (string, error) {
+	resp, err := http.Get("https://api.example.com/data")
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+	body, _ := io.ReadAll(resp.Body)
+	return string(body), nil
+}
+
+func myWorkflow(ctx dbos.DBOSContext, input string) (string, error) {
+	data, err := dbos.RunAsStep(ctx, fetchData, dbos.WithStepName("fetchData"))
+	if err != nil {
+		return "", err
+	}
+	return data, nil
+}
+```
+
+`dbos.RunAsStep` can also accept an inline closure:
+
+```go
+func myWorkflow(ctx dbos.DBOSContext, input string) (string, error) {
+	data, err := dbos.RunAsStep(ctx, func(ctx context.Context) (string, error) {
+		resp, err := http.Get("https://api.example.com/data")
+		if err != nil {
+			return "", err
+		}
+		defer resp.Body.Close()
+		body, _ := io.ReadAll(resp.Body)
+		return string(body), nil
+	}, dbos.WithStepName("fetchData"))
+	return data, err
+}
+```
+
+Step type signature: `type Step[R any] func(ctx context.Context) (R, error)`
+
+Step requirements:
+- The function must accept a `context.Context` parameter — use the one provided, not the workflow's context
+- Inputs and outputs must be serializable to JSON
+- Cannot start or enqueue workflows from within steps
+- Calling a step from within another step makes the inner call part of the outer step's execution
+
+When to use steps:
+- API calls to external services
+- File system operations
+- Random number generation
+- Getting current time
+- Any non-deterministic operation
+
+Reference: [DBOS Steps](https://docs.dbos.dev/golang/tutorials/step-tutorial)