docs(operations): add production cluster runbook guidance

[ReubenBond]

Problem

Operators need practical guidance for managing Orleans after initial deployment, including configuration changes, routine maintenance, recovery exercises, and incident runbooks.

Solution

Add a production operations guide that defines responsibility boundaries across the host, Orleans runtime, providers, and application. Document environment records, change classification, bounded configuration rollout with observability gates and rollback compatibility, safe maintenance sequencing, operational exercises, and minimum runbook content, then link the guide from the deployment hub, readiness checklist, and navigation.

Rationale

A focused operator workflow connects the existing upgrade, shutdown, observability, configuration, and rollback material without duplicating those detailed guides. It makes Orleans runtime guarantees and deployment-environment responsibilities explicit for production change control.

Closes #3228

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull request overview

Adds a new operations-focused guide to help production operators manage Orleans clusters after initial deployment (configuration changes, maintenance, recovery exercises, and incident/runbook preparation) and wires it into the existing deployment documentation navigation.

Changes:

• Adds a new “Operate a production cluster” production operations guide with concrete guidance on configuration control, maintenance sequencing, operational exercises, and runbook content.
• Links the new guide from the deployment hub and updates the production-readiness checklist to reference it.
• Adds the guide to the docs navigation (TOC) under “Deploy and operate”.

Show a summary per file

File	Description
docs/site/src/content/docs/toc.yml	Adds the new production operations guide to the “Deploy and operate” navigation section.
docs/site/src/content/docs/deployment/production-readiness.md	Updates the checklist to point operators to the new production operations guidance/runbook expectations.
docs/site/src/content/docs/deployment/production-operations.md	Introduces the new production operations/runbook guidance document.
docs/site/src/content/docs/deployment/index.md	Links the new guide from the deployment “Operations track” hub page.

Review details

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• Files reviewed: 4/4 changed files
• Comments generated: 0
• Review effort level: Lite