chore: release v4.0.0 - sync 550+ skills and restructure docs

skills/airflow-dag-patterns/SKILL.md

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+---
+name: airflow-dag-patterns
+description: Build production Apache Airflow DAGs with best practices for operators, sensors, testing, and deployment. Use when creating data pipelines, orchestrating workflows, or scheduling batch jobs.
+---
+
+# Apache Airflow DAG Patterns
+
+Production-ready patterns for Apache Airflow including DAG design, operators, sensors, testing, and deployment strategies.
+
+## Use this skill when
+
+- Creating data pipeline orchestration with Airflow
+- Designing DAG structures and dependencies
+- Implementing custom operators and sensors
+- Testing Airflow DAGs locally
+- Setting up Airflow in production
+- Debugging failed DAG runs
+
+## Do not use this skill when
+
+- You only need a simple cron job or shell script
+- Airflow is not part of the tooling stack
+- The task is unrelated to workflow orchestration
+
+## Instructions
+
+1. Identify data sources, schedules, and dependencies.
+2. Design idempotent tasks with clear ownership and retries.
+3. Implement DAGs with observability and alerting hooks.
+4. Validate in staging and document operational runbooks.
+
+Refer to `resources/implementation-playbook.md` for detailed patterns, checklists, and templates.
+
+## Safety
+
+- Avoid changing production DAG schedules without approval.
+- Test backfills and retries carefully to prevent data duplication.
+
+## Resources
+
+- `resources/implementation-playbook.md` for detailed patterns, checklists, and templates.