Add OCI networking landing zones skill

[shyam2511]

Summary

Adds an OCI Networking Landing Zones Terraform skill, following the directory pattern established by #111.

The skill supports safe, module-constrained Terraform configuration for:

• VCNs and subnets
• Route tables and internet, NAT, and service gateways
• Security lists, rules, network security groups, and NSG rules
• ZPR security-attribute assignments

It uses only oci-landing-zones/terraform-oci-modules-networking, preserves existing Terraform and pipeline conventions, validates OCI resources with read-only MCP operations when available, and explicitly avoids local Terraform execution and ZPR policy management.

Changes

• Add terraform-oci-modules-networking-skill under oci/oci-landing-zone-terraform-module/
• Include skill instructions, agent metadata, and support/input/validation/lifecycle references
• Add OCI skill routing, scope boundaries, and source documentation

Validation

• Ran git diff --check
• Confirmed the imported skill files match the supplied source, excluding the source-only archive and local metadata file