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-python/references/step-basics.md

@@ -0,0 +1,53 @@
+---
+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):**
+
+```python
+import requests
+
+@DBOS.workflow()
+def my_workflow():
+    # External API call directly in workflow - not checkpointed!
+    response = requests.get("https://api.example.com/data")
+    return response.json()
+```
+
+**Correct (external call in step):**
+
+```python
+import requests
+
+@DBOS.step()
+def fetch_data():
+    response = requests.get("https://api.example.com/data")
+    return response.json()
+
+@DBOS.workflow()
+def my_workflow():
+    # Step result is checkpointed for recovery
+    data = fetch_data()
+    return data
+```
+
+Step requirements:
+- Inputs and outputs must be serializable
+- Should not modify global state
+- Can be retried on failure (configurable)
+
+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/python/tutorials/step-tutorial)