feat(engineering-team): add snowflake-development skill

Snowflake SQL, data pipelines (Dynamic Tables, Streams+Tasks), Cortex AI,
Snowpark Python, dbt integration. Includes 3 practical workflows, 9
anti-patterns, cross-references, and troubleshooting guide.

- SKILL.md: 294 lines (colon-prefix rule, MERGE, DTs, Cortex AI, Snowpark)
- Script: snowflake_query_helper.py (MERGE, DT, RBAC generators)
- References: 3 files (SQL patterns, Cortex AI/agents, troubleshooting)

Based on PR #416 by James Cha-Earley — enhanced with practical workflows,
anti-patterns section, cross-references, and normalized frontmatter.

Co-Authored-By: James Cha-Earley <jamescha-earley@users.noreply.github.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mkdocs.yml

@@ -161,6 +161,7 @@ nav:
       - "Senior SecOps Engineer": skills/engineering-team/senior-secops.md
       - "Senior Security Engineer": skills/engineering-team/senior-security.md
       - "Security Pen Testing": skills/engineering-team/security-pen-testing.md
+      - "Snowflake Development": skills/engineering-team/snowflake-development.md
       - "Stripe Integration Expert": skills/engineering-team/stripe-integration-expert.md
       - "TDD Guide": skills/engineering-team/tdd-guide.md
       - "Tech Stack Evaluator": skills/engineering-team/tech-stack-evaluator.md