Add Workday Developer agent skills suite

[srivilliamsai]

What this PR adds or changes

Adds an 8-skill agent skills suite under examples/ that teaches AI agents and Developer Copilots how to review, scaffold, and validate Workday Extend, PMD, Home Cards, Orchestrate, APIs, and AI Gateway artifacts according to enterprise best practices.

Checklist for new or changed examples

• The example lives entirely in its own folder under examples/
• node scripts/validate-examples.mjs --check passes (valid example.json, README present, index table in sync)
• The README says what the artifact is, how to use it, and what to change before deploying it (the "Before you deploy" section)
• No credentials, tenant names, or real personal data anywhere in the folder
• node scripts/audit-examples.mjs --changed passes, or the findings it reports are explained below

Anything reviewers should know?

• Covers: workday-skill, workday-developer-copilot-skill, workday-extend-skill, workday-pmd-skill, workday-home-cards-skill, workday-orchestrate-skill, workday-apis-skill, and workday-ai-gateway-skill.
• All 8 examples passed Arcane Auditor v2.0.0 and Hub rules with 0 findings (0 ACTION / 0 ADVICE).

[github-actions]

Example audit

Audited examples/workday-ai-gateway-skill, examples/workday-apis-skill, examples/workday-developer-copilot-skill, examples/workday-extend-skill, examples/workday-home-cards-skill, examples/workday-orchestrate-skill, examples/workday-pmd-skill, examples/workday-skill. No findings. Thank you for a clean submission.

Run it yourself: ./scripts/install-arcane.sh once, then node scripts/audit-examples.mjs --changed. Rule explanations and fixes: docs/EXAMPLE_BEST_PRACTICES.md.