docs: \"Operate your Trinity in 5 minutes\" onboarding quickstart for the ops starter

[vybe]

Summary

Write a getting-started quickstart that takes a first-time operator from zero to a running ops/DevOps starter agent in ~5 minutes, with copy-paste steps and a set of sample ops prompts ("check fleet health", "show me recent errors", "update and roll back if it fails").

Context

The starter agents only drive adoption if the path to using them is obvious. A focused quickstart + prompt cookbook is the front door for new operators and the reference the deploy flows link to.

Acceptance Criteria

• Quickstart under docs/user-docs/ covering connect → deploy ops starter → first ops command
• Sample ops prompt cookbook (health, logs, updates, rollback, provisioning)
• Uses placeholder values only (your-domain.com, ${MCP_API_KEY}, user@example.com) — no real hosts, emails, or secrets
• Linked from the relevant deploy/onboarding entry points

Technical Notes

• Cross-link abilityai/trinity-ops-public and the abilities trinity plugin skills (/trinity:connect, /trinity:onboard, /trinity:deploy-new-instance).

Parent epic: ops/DevOps starter agents for one-click instance management.