Platform operational improvements, addon enablement, and extensibility

## Overview

This iteration covers hardcoded value cleanup, addon verification, new cluster providers, and future extensibility for the GitOps addon management platform.

### Completed (prior iteration):
- clusterName-based prefixing for all infrastructure IAM roles/policies
- PostSync restart hook for pod identity credential injection
- Config split (template + local override) with JSON schema
- Destroy ordering fix (cluster before providers)
- Hub fleet-secret separated from spoke pipeline
- Addon charts aligned to use `clusterName` instead of `resourcePrefix`
- Spoke clusters provisioned (spoke-dev, spoke-prod) with composition fixes
- Abstractions AppSet for automatic XRD/composition deployment
- `task seed-spoke` command for spoke Secrets Manager seeding
- ArgoCD AccessEntry on spokes via composition
- Destroy flow scans all environment enabled-addons

### Sub-Issues

- [ ] #585 — Remove hardcoded static values from addon charts (High)
- [x] #586 — Enable and verify core addons (High)
- [x] #587 — Enable and verify gitops addons (Medium)
- [x] #588 — Enable and verify security addons (Medium)
- [ ] #589 — Enable and verify observability addons (Medium)
- [ ] #590 — Enable and verify platform addons (Medium)
- [x] #591 — Enable and verify ML/AI addons (Medium)
- [ ] #592 — Add Terraform cluster provider (Medium)
- [ ] #593 — Standardize root Taskfile bootstrap contract (Medium)
- [ ] #594 — Remove ArgoCD capability Job when Crossplane supports it (Low)
- [ ] #595 — Add agentic AI addons (Medium)
- [ ] #596 — Create dedicated EKS Auto Mode nodepools (Medium)
- [ ] #597 — KRO resource groups — align naming with clusterName (Medium)
- [ ] #598 — Spoke cluster end-to-end validation (Medium)
- [ ] #599 — Remove resourcePrefix from config.yaml (Low)
- [x] #600 — Create PlatformCluster using KRO + ACK (Medium)
- [ ] #601 — Pluggable composition backends (Low)
- [ ] #602 — Automate spoke Secrets Manager seeding via composition (Medium)
- [ ] #603 — Move config secrets to Parameter Store (Medium)
- [ ] #604 — Support private git repos with GitHub App/token (High)
- [ ] #606 — Create spoke pod identities on hub via composition (High)

**Branch:** `feature/resourcePrefix` → `feature/agent-platform`
**PR:** #583