chore: Improve review-spec-update skill

[davidkna-sap]

Context

Closes SAP/ai-sdk-js-backlog#ISSUENUMBER.
This changes improves compliance with proposed architecture decisions.

What this PR does and why it is needed

[hyperspace-insights]

Summary

The following content is AI-generated and provides a summary of the pull request:

---

Context

This PR improves the review-spec-update skill to better align with proposed architecture decisions for spec-driven development.

What this PR does and why it is needed

Enhances the SKILL.md guide for reviewing spec updates with additional classification rules and a more complete quick checklist. Key improvements include:

• New breaking-change rules added to the classification tables:

  • additionalProperties: false added to a request object → breaking
  • Changes to under-specified response objects ({}) → non-breaking
  • Shared schema splits (e.g. FooConfig → FooConfigInput + FooConfigOutput) → SDK-effort only unless the old type was exported

• New "Schema-split impact check" section with a step-by-step guide for assessing downstream impact when a schema is split, including an illustrative example

• Updated quick checklist with three new items:

  • additionalProperties: false additions require a [compat] changeset
  • Schema splits: exported old names need [compat]; unexported + no structural change → no action
  • Under-specified response changes confirmed as non-breaking and omitted from [compat]

• Perspective callout clarifying the distinction between user-breaking changes (requiring [compat] changesets) and SDK-effort-only changes

Category: Chore

---

• 🔄 Regenerate and Update Summary
• ✏️ Insert as PR Description (deletes this comment)
• 🗑️ Delete comment

PR Bot Information

Version: 1.26.14

• Output Template: Repository PR Template
• File Content Strategy: Full file content
• Summary Prompt: Default Prompt
• Event Trigger: pull_request.ready_for_review
• LLM: anthropic--claude-4.6-sonnet
• Correlation ID: 87758070-76bc-11f1-95be-85329fc04c00