Align frontmatter with Agent Skills spec

[marc0olo]

Summary

• Migrate all 13 skills to Agent Skills spec-compliant frontmatter: name, description, license, compatibility, metadata.title, metadata.category
• Remove non-spec fields: version, endpoints, status, dependencies, requires, tags
• Delete ai-plugin.json endpoint and generate-readme-table.js script
• Simplify CI, validator, site components, and all documentation
• Add Apache-2.0 LICENSE file
• Net -404 lines across 33 files

Changes by area

Frontmatter (all 13 skills + template + schema):
New format:

name: ckbtc
description: "..."
license: Apache-2.0
compatibility: "icp-cli >= 0.1.0"
metadata:
  title: ckBTC Integration
  category: DeFi

Site:

• Remove version badge, endpoints count, status badge, dependency links from browse/detail pages
• Remove redundant Before/After section from How It Works page
• Align anatomy section with README structure table (6 rows, same names)
• Remove redundant Quick Start terminal from Access page
• Fix header width jumping between pages (consistent 1200px nav)
• Fix "Versioned in frontmatter" → "Git-tracked with last-updated dates"

Docs (README, CONTRIBUTING, CLAUDE.md):

• Collapse Usage from ~80 lines (per-agent sections) to ~12 lines (CLI + manual)
• Downgrade unknown categories from error to warning
• Relax body sections to recommendations (warnings), not requirements (errors)
• Slim template from 145 to 68 lines (guidance comments instead of skeleton code)

CI & tooling:

• Simplify _checks.yml from 3 steps to 1 (npm ci + node scripts/validate-skills.js)
• Remove generate script from package.json, update build to validate && astro build
• Delete scripts/generate-readme-table.js
• Delete src/pages/.well-known/ai-plugin.json.ts

Closes #45

[marc0olo]

Update: compatibility vs Prerequisites clarification

Added two commits clarifying the compatibility field:

• compatibility = environment requirements (tools, system packages, network access) — aligned with the Agent Skills spec definition
• ## Prerequisites = library/SDK dependencies (language-specific crates, npm packages, mops packages)

Updated the template, CONTRIBUTING.md, and CLAUDE.md to reflect this distinction clearly.

Follow-up needed: 3 skills (ckbtc, evm-rpc, internet-identity) have minor version gaps in their Prerequisites sections (libraries listed without minimum versions). This will be addressed in a separate PR that makes all skills consistent.