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-transactions.md

@@ -0,0 +1,58 @@
+---
+title: Use Transactions for Database Operations
+impact: HIGH
+impactDescription: Transactions provide atomic database operations
+tags: transaction, database, postgres, sqlalchemy
+---
+
+## Use Transactions for Database Operations
+
+Transactions are a special type of step optimized for database access. They execute as a single database transaction. Only use with Postgres.
+
+**Incorrect (database access in regular step):**
+
+```python
+@DBOS.step()
+def save_to_db(data):
+    # For Postgres, use transactions instead of steps
+    # This doesn't get transaction guarantees
+    engine.execute("INSERT INTO table VALUES (?)", data)
+```
+
+**Correct (using transaction):**
+
+```python
+from sqlalchemy import text
+
+@DBOS.transaction()
+def save_to_db(name: str, value: str) -> None:
+    sql = text("INSERT INTO my_table (name, value) VALUES (:name, :value)")
+    DBOS.sql_session.execute(sql, {"name": name, "value": value})
+
+@DBOS.transaction()
+def get_from_db(name: str) -> str | None:
+    sql = text("SELECT value FROM my_table WHERE name = :name LIMIT 1")
+    row = DBOS.sql_session.execute(sql, {"name": name}).first()
+    return row[0] if row else None
+```
+
+With SQLAlchemy ORM:
+
+```python
+from sqlalchemy import Table, Column, String, MetaData, select
+
+greetings = Table("greetings", MetaData(),
+    Column("name", String),
+    Column("note", String))
+
+@DBOS.transaction()
+def insert_greeting(name: str, note: str) -> None:
+    DBOS.sql_session.execute(greetings.insert().values(name=name, note=note))
+```
+
+Important:
+- Only use transactions with Postgres databases
+- For other databases, use regular steps
+- Never use `async def` with transactions
+
+Reference: [DBOS Transactions](https://docs.dbos.dev/python/reference/decorators#transactions)