feat: add 8 service skills for full MCP server parity

[notque]

Summary

• Add 8 new service skills covering all MCP server services that previously lacked toolkit coverage
• Update README skills table and plugin description to reflect 18-service coverage
• Toolkit now has 18 skills covering all 18 MCP server services (55 tools)

New Skills

Skill	Service	Tools Covered
sapcc-dns	Designate	designate_list_zones, designate_get_zone, designate_list_recordsets
sapcc-secrets	Barbican	barbican_list_secrets, barbican_get_secret
sapcc-object-storage	Swift	swift_list_containers, swift_list_objects, swift_get_object_metadata
sapcc-filesystems	Manila	manila_list_shares, manila_get_share
sapcc-loadbalancer	Octavia	octavia_list_loadbalancers, octavia_get_loadbalancer, octavia_list_listeners, octavia_list_pools
sapcc-images	Glance	glance_list_images, glance_get_image
sapcc-baremetal	Ironic	ironic_list_nodes, ironic_get_node
sapcc-autoscaling	Castellum	castellum_get_project_resources, castellum_list_pending_operations, castellum_list_recently_failed_operations

Pattern

Each skill follows the established format:

• YAML frontmatter (name, description with triggers, version, metadata)
• MCP Tools table with parameters and return fields
• Numbered Gotchas (service-specific agent mistake prevention)
• Common Workflows (step-by-step using MCP tools)
• Troubleshooting (failure modes with diagnostic steps)
• Security Considerations
• Cross-Service References table

Validation

• python3 tools/validate.py passes (all 18 skills validated)
• All tool references verified against MCP server tool inventory (zero phantom references)

Test plan

• python3 tools/validate.py passes
• Each skill loads in Claude Code and triggers correctly on keyword match
• Cross-service references point to real tools