docs: tooling API style guide

[chris-de-leon-cll]

Add Tooling API Style Guide

Summary

This PR adds a Changeset Style Guide under deployment/docs/. The document captures recurring review feedback as explicit rules, short rationale, and before/after Go examples. It is meant to improve new changesets and code you are already editing, not to force broad rewrites of legacy code that is already correct and safe to operate.

What’s in the guide

The guide covers practical topics that show up often in deployment changeset review. The techniques in the guide will allow you to write changests that are:

• Safe to retry
• Easy to operate
• Hard to misconfigure
• Consistent with repo conventions
• Explicit about failure modes
• Minimal in abstraction and validation

How reviewers and authors can use it

• While authoring: apply the rules to inputs, defaults, ref resolution, and apply behavior early.
• Before review: run the checklist to catch retry hazards, stale reads, inconsistent conventions, and unnecessary abstraction.

Notes

• When a recommendation conflicts with established conventions in a file, the guide recommends preferring local consistency unless there is a clear correctness, safety, or operability reason not to.

[Copilot]

Pull request overview

Adds a new Changeset Style Guide document to capture recurring review feedback as explicit rules, rationale, and before/after examples to improve the safety and operability of deployment changesets.

Changes:

• Introduces a “Changeset Style Guide” under deployment/docs/ with practical rules (idempotency, ref resolution, defaults, cached reads, qualifiers, validation).
• Provides a review checklist to standardize pre-review self-checks.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[github-actions]

Metric	docs/tooling-api-style-guide	main
Coverage	70.1%	69.8%

[RayXpub]

q: isn't this already handled at the operations level by the operations API though?