EPIC: Incorporate NGINX Agent v3 content into NGINX One docs

[travisamartin]

Goal

Document NGINX Agent v3 in the NGINX One (N1) documentation set using Hugo include files. Surface installation, connection, and migration steps directly within the N1 docs so users can stay in context without switching to a separate doc set.

Background

• NGINX Agent is a daemon, not a standalone product. Its documentation should live inside related product documentation like NGINX One and (eventually) NGINX Instance Manager.
• To support this, we’ll maintain NGINX Agent steps as Hugo include files in the NGINX documentation repository.
• These will be referenced in the N1 docs — both in onboarding flows and in a dedicated "NGINX Agent" section.
• Goal: write once, reuse where needed. The NGINX Agent team maintains the content; the N1 team surfaces it in appropriate contexts.

Tasks

1. Content Development

Create Hugo include files under /content/includes/nginx-agent/:

• install-from-script.md
• install-from-noss-repo.md
• install-from-nginx-plus-repo.md
• connect-to-n1-console.md
• migrate-v2-to-v3.md
• uninstall.md
• tech-specs.md (or reference existing shared content if available)

Each include should:

• Be task-focused and written in plain language (following F5 Modern Voice and NGINX style guides)
• Use consistent formatting, structure, and metadata
• Include any required configuration or platform-specific notes

2. Navigation Update

Add a new top-level section in the NGINX One documentation nav:

.
└── NGINX Agent
    ├── Tech specs
    ├── Install from NGINX Open Source repo
    ├── Install from NGINX Plus repo
    ├── Connect NGINX instances to NGINX One console
    ├── Migrate from NGINX Agent v2 to v3
    └── Uninstall NGINX Agent

Each topic should reference the appropriate include file.

3. Contextual Reuse

• Reference the script-based install include (install-from-script.md) in Get started > Installing NGINX Agent — this is the default onboarding path for fast 0→1 setup
• Reuse migration and connection includes in other workflows as needed

4. Out of Scope

• Do not document install from GitHub repo at this time

[mjang]

I assigned @JTorreG as he demo'd a layout earlier