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/workflow-constraints.md

@@ -0,0 +1,70 @@
+---
+title: Follow Workflow Constraints
+impact: CRITICAL
+impactDescription: Violating constraints causes failures or incorrect behavior
+tags: workflow, step, constraints, rules
+---
+
+## Follow Workflow Constraints
+
+DBOS workflows and steps have specific constraints that must be followed for correct operation.
+
+**Incorrect (calling start_workflow from step):**
+
+```python
+@DBOS.step()
+def my_step():
+    # Never start workflows from inside a step!
+    DBOS.start_workflow(another_workflow)
+```
+
+**Incorrect (modifying global state):**
+
+```python
+results = []  # Global variable
+
+@DBOS.workflow()
+def my_workflow():
+    # Don't modify globals from workflows!
+    results.append("done")
+```
+
+**Incorrect (using recv outside workflow):**
+
+```python
+@DBOS.step()
+def my_step():
+    # recv can only be called from workflows!
+    msg = DBOS.recv("topic")
+```
+
+**Correct (following constraints):**
+
+```python
+@DBOS.workflow()
+def parent_workflow():
+    result = my_step()
+    # Start child workflow from workflow, not step
+    handle = DBOS.start_workflow(child_workflow, result)
+    # Use recv from workflow
+    msg = DBOS.recv("topic")
+    return handle.get_result()
+
+@DBOS.step()
+def my_step():
+    # Steps just do their work and return
+    return process_data()
+
+@DBOS.workflow()
+def child_workflow(data):
+    return transform(data)
+```
+
+Key constraints:
+- Do NOT call `DBOS.start_workflow` from a step
+- Do NOT call `DBOS.recv` from a step
+- Do NOT call `DBOS.set_event` from outside a workflow
+- Do NOT modify global variables from workflows or steps
+- Do NOT use threads to start workflows
+
+Reference: [DBOS Workflows](https://docs.dbos.dev/python/tutorials/workflow-tutorial)