Add arn-spark, arn-code, and arn-infra (Arness plugin marketplace)

[fredcallagan]

Adds Arness, an open-source plugin marketplace for Claude Code with three plugins covering greenfield exploration, development pipeline, and infrastructure provisioning. Repository: https://github.com/AppsVortex/arness (MIT). Install via /plugin marketplace add AppsVortex/arness, then /plugin install <plugin-name>@arn-marketplace.

arn-spark (Developer Productivity)

Adds arn-spark to the Developer Productivity section.

• 28 skills for product discovery with persona generation, brand naming with trademark screening, architecture vision, use case authoring, project scaffolding
• Visual style exploration, static prototype validation, clickable prototype validation, feature extraction
• Stress-testing suite (PR/FAQ, pre-mortem, competitive gap, synthetic interviews) and concept review to merge findings back into the spec
• Artifact-driven contract between stages; local-only, no telemetry

arn-code (Developer Productivity)

Adds arn-code to the Developer Productivity section.

• 35 skills for feature spec generation, phased planning, plan-writer + plan-reviewer
• task-executor + task-reviewer agents per task with self-healing test loops
• sketch (UI preview before code), assess (PR review with test gate)
• 3 ceremony tiers: swift, standard, thorough, selected per change scope
• Artifact-driven contract between stages; local-only, no telemetry

arn-infra (DevOps & Performance)

Adds arn-infra to the DevOps & Performance section.

• 25 skills for containerization (Dockerfile), IaC generation (OpenTofu/Terraform), deployment, CI/CD pipelines
• Environment management, secrets, monitoring, migration between providers
• Structured change management with phased rollback checkpoints
• Security audit via Checkov and Trivy; cost analysis via Infracost
• Local-only, no telemetry, no server component