feat: add agent-led OpenHands Enterprise Replicated install skill

[rajshah4]

Summary

Adds install-openhands-replicated, a customer-neutral skill for guiding supported OpenHands Enterprise VM installations delivered with Replicated Embedded Cluster.

This implements the first milestone of internal tracker PRD-137:

• read-only host, DNS, TLS, outbound, and LLM endpoint preflight
• AWS Terraform or manual VM scoping
• provider authentication guidance for GitHub, GitLab, Bitbucket Data Center, and Azure DevOps
• guided Replicated installer and Admin Console steps
• explicit approval gates for mutating or secret-bearing operations
• core product, integration, storage, backup, and operator-handoff validation
• reusable IT request templates and a non-secret install planning asset

Safety boundary

The skill does not claim a fully headless installation. Headless automation remains conditional on a documented, release-specific installer schema and supported secret-input mechanism. The current workflow uses guided installer/Admin Console ClickOps and preview-first documented KOTS configuration.

Validation

• uv run python scripts/sync_extensions.py --check
• official skill validator
• Bash syntax checks
• ShellCheck across all bundled scripts
• deterministic DNS, KOTS preview, outbound argument, copy-identity, privacy, and diff checks
• uv run pytest -q: 540 passed, 6 skipped

Registry updates

• registers the skill in the environment category
• adds OpenHands/Claude/Codex plugin metadata
• regenerates the README catalog and skills/index.js
• updates the expected skill-category count

This draft pull request was created by an AI agent (OpenHands) on behalf of Rajiv Shah.