feat: add Agent Skills and restructure documentation

- Add 47 Agent Skills across 14 plugins following Anthropic's specification
  - Python (5): async patterns, testing, packaging, performance, UV package manager
  - JavaScript/TypeScript (4): advanced types, Node.js patterns, testing, modern JS
  - Kubernetes (4): manifests, Helm charts, GitOps, security policies
  - Cloud Infrastructure (4): Terraform, multi-cloud, hybrid networking, cost optimization
  - CI/CD (4): pipeline design, GitHub Actions, GitLab CI, secrets management
  - Backend (3): API design, architecture patterns, microservices
  - LLM Applications (4): LangChain, prompt engineering, RAG, evaluation
  - Blockchain/Web3 (4): DeFi protocols, NFT standards, Solidity security, Web3 testing
  - Framework Migration (4): React, Angular, database, dependency upgrades
  - Observability (4): Prometheus, Grafana, distributed tracing, SLO
  - Payment Processing (4): Stripe, PayPal, PCI compliance, billing
  - API Scaffolding (1): FastAPI templates
  - ML Operations (1): ML pipeline workflow
  - Security (1): SAST configuration

- Restructure documentation into /docs directory
  - agent-skills.md: Complete guide to all 47 skills
  - agents.md: All 85 agents with model configuration
  - plugins.md: Complete catalog of 63 plugins
  - usage.md: Commands, workflows, and best practices
  - architecture.md: Design principles and patterns

- Update README.md
  - Add Agent Skills banner announcement
  - Reduce length by ~75% with links to detailed docs
  - Add What's New section showcasing Agent Skills
  - Add Popular Use Cases with real examples
  - Improve navigation with Core Guides and Quick Links

- Update marketplace.json with skills arrays for 14 plugins

All 47 skills follow Agent Skills Specification:
- Required YAML frontmatter (name, description)
- Use when activation clauses
- Progressive disclosure architecture
- Under 1024 character descriptions

plugins/kubernetes-operations/skills/helm-chart-scaffolding/assets/Chart.yaml.template

@@ -0,0 +1,42 @@
+apiVersion: v2
+name: <chart-name>
+description: <Chart description>
+type: application
+version: 0.1.0
+appVersion: "1.0.0"
+
+keywords:
+  - <keyword1>
+  - <keyword2>
+
+home: https://github.com/<org>/<repo>
+
+sources:
+  - https://github.com/<org>/<repo>
+
+maintainers:
+  - name: <Maintainer Name>
+    email: <maintainer@example.com>
+    url: https://github.com/<username>
+
+icon: https://example.com/icon.png
+
+kubeVersion: ">=1.24.0"
+
+dependencies:
+  - name: postgresql
+    version: "12.0.0"
+    repository: "https://charts.bitnami.com/bitnami"
+    condition: postgresql.enabled
+    tags:
+      - database
+  - name: redis
+    version: "17.0.0"
+    repository: "https://charts.bitnami.com/bitnami"
+    condition: redis.enabled
+    tags:
+      - cache
+
+annotations:
+  category: Application
+  licenses: Apache-2.0