[feat] New skill: principle-cost-awareness

[lugassawan]

Goal

A principle-cost-awareness skill encodes cloud cost engineering principles so agents can surface cost-impacting decisions during design and code review.

Motivation

Cloud cost is an engineering concern, not just a finance concern. Egress charges, over-provisioned instances, and chattiness between services can multiply a bill by 10× without any visible correctness failure. No principle skill addresses this domain.

Surface

• Skill — principle-*

Sketch (optional)

File: skills/principle-cost-awareness/SKILL.md

Key topics:

• FinOps mindset: cost is a feature requirement
• Egress costs (the most common surprise)
• Instance right-sizing and auto-scaling tradeoffs
• Scale-to-zero patterns and cold-start tradeoffs
• Cost-per-request mental model for API design
• Storage tier selection (hot vs warm vs cold)
• Logging and observability cost (log volume, sampling strategies)
• Identifying "chatty" service interactions that inflate request count

Acceptance (optional)

• skills/principle-cost-awareness/SKILL.md exists with valid frontmatter
• scripts/validate.py passes