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/advanced-versioning.md

@@ -0,0 +1,66 @@
+---
+title: Use Versioning for Blue-Green Deployments
+impact: LOW
+impactDescription: Safely deploy new code with version tagging
+tags: versioning, blue-green, deployment, recovery
+---
+
+## Use Versioning for Blue-Green Deployments
+
+DBOS versions workflows to prevent unsafe recovery. Use blue-green deployments to safely upgrade.
+
+**Incorrect (deploying breaking changes without versioning):**
+
+```python
+# Deploying new code directly kills in-progress workflows
+# because their checkpoints don't match the new code
+
+# Old code
+@DBOS.workflow()
+def workflow():
+    step_a()
+    step_b()
+
+# New code replaces old immediately - breaks recovery!
+@DBOS.workflow()
+def workflow():
+    step_a()
+    step_c()  # Changed step - old workflows can't recover
+```
+
+**Correct (using versioning with blue-green deployment):**
+
+```python
+# Set explicit version in config
+config: DBOSConfig = {
+    "name": "my-app",
+    "application_version": "2.0.0",  # New version
+}
+DBOS(config=config)
+
+# Deploy new version alongside old version
+# New traffic goes to v2.0.0, old workflows drain on v1.0.0
+
+# Check for remaining old workflows before retiring v1.0.0
+old_workflows = DBOS.list_workflows(
+    app_version="1.0.0",
+    status=["PENDING", "ENQUEUED"]
+)
+
+if len(old_workflows) == 0:
+    # Safe to retire old version
+    pass
+```
+
+Fork a workflow to run on a new version:
+
+```python
+# Fork workflow from step 5 on version 2.0.0
+new_handle = DBOS.fork_workflow(
+    workflow_id="old-workflow-id",
+    start_step=5,
+    application_version="2.0.0"
+)
+```
+
+Reference: [Versioning](https://docs.dbos.dev/python/tutorials/upgrading-workflows#versioning)