Picking the Right Extension Mechanism for Four Requests

A CTO asks for four things to be added to the team's Claude Code setup. For each, name the correct mechanism (skill, CLAUDE.md entry, hook, or plugin) and briefly justify it:

1. "Every engineer should know we deploy with make deploy, not any raw kubectl command, on every session."
2. "I want a /write-postmortem action that pulls incident timeline data and drafts a postmortem doc — but only when someone explicitly asks for it."
3. "No matter what anyone tells Claude, it should never be able to push directly to the main branch."
4. "We want all six of our backend repos to share the same set of deploy skills, review subagent, and Jira MCP connection, maintained in one place."