Add workflow-first Enterprise VM installation skill

[rajshah4]

Desired Behavior

Operators have a workflow-first OpenHands Enterprise VM installation skill that keeps official documentation authoritative while adding safety gates, reusable preflights, support escalation, end-to-end validation, and handoff evidence.

Acceptance Criteria

• The skill notes synchronization with current official Enterprise documentation.
• The read-only Kubernetes warning is prominent.
• Volatile sizing tables, field catalogs, and installer screens are not duplicated.
• Host, DNS, TLS, outbound, storage, and integration checks remain executable.
• Support-only KOTS changes fail closed.
• Skill validation and repository tests pass.

Context

This tracks the workflow-first installation skill implemented by PR #458.

This issue was updated by an AI agent (OpenHands) on behalf of Rajiv Shah.

[github-actions]

⚠️ Not yet ready-for-dev

This issue does not yet meet the readiness criteria, so the
ready-for-dev label has not been applied (or has been removed).
The criteria are type-specific:

Bug reports (bug label):

• The ### Actual Behavior section must describe reproducible steps
  and include a command such as uv run pytest, pytest, python,
  pip, npm run, or node.
• An ### Acceptance Criteria section with at least one checklist item (- [ ] ...).

Enhancements (enhancement label):

• A ### Desired Behavior section.
• An ### Acceptance Criteria section with at least one checklist item.

What is missing:

• The issue has neither the bug nor enhancement label, so its readiness criteria cannot be evaluated. Add the appropriate label.

Edit the issue to address the gaps and the ready-for-dev label will be
applied automatically.

This is an automated readiness check posted by a workflow.