feat: add fusion-help skills and fix Windows validation scripts

[HansDahle]

Why

Adds three Fusion Help skills from the global skill library into the repository catalog, and fixes Windows compatibility issues in validation scripts discovered during the process.

Current behavior

• The repository has no Fusion Help-related skills.
• Validation scripts (extractFrontmatter, parseFrontmatter, discoverLocalSkills) assume Unix line endings and forward-slash paths, causing failures on Windows.

New behavior

• Three new skills are available in skills/:
  • fusion-help-api — guides developers through direct Fusion Help REST API interaction (articles, FAQs, release notes, search, content management)
  • fusion-help-docs — guides app teams through authoring and publishing help documentation using the fusion-help-cli
  • fusion-help-integration — wires Fusion Help Center into app pages via useHelpCenter hook and PageLayout props
• Validation scripts work correctly on both Windows and Unix:
  • extractFrontmatter handles \r\n line endings
  • parseFrontmatter splits on \r?\n instead of \n
  • discoverLocalSkills strips both / and \ before SKILL.md

References

• Issue(s): —
• Related PR(s): —
• Docs / specs: —

Reviewer focus

• Start here (files/areas): skills/fusion-help-api/, skills/fusion-help-docs/, skills/fusion-help-integration/
• Verify these behavior changes: new skills appear in npx -y skills add . --list; bun run validate:skills and bun run validate:ownership pass on Windows
• Risky or security-sensitive parts: validation regex changes in scripts/list-skills/ and scripts/validate-skills/

Self review checklist

• I scoped this PR to one clear purpose.
• I followed CONTRIBUTING.md.
• I did not include secrets, credentials, or sensitive data.
• I reviewed my own diff for clarity and unintended changes.

[github-actions]

Changeset summary

Detected 4 changeset file(s):

.changeset/add-fusion-help-api.md:

---
"fusion-help-api": patch
---

Add fusion-help-api skill

- Guides developers through direct Fusion Help REST API interaction
- Covers articles, FAQs, release notes, search, and content management

.changeset/add-fusion-help-docs.md:

---
"fusion-help-docs": patch
---

Add fusion-help-docs skill

- Guides app teams through authoring and publishing help documentation using fusion-help-cli
- Covers articles, release notes, and FAQs

.changeset/add-fusion-help-integration.md:

---
"fusion-help-integration": patch
---

Add fusion-help-integration skill

- Wires Fusion Help Center into app pages via useHelpCenter hook and PageLayout props
- Creates article slug constants and connects contextual help articles

.changeset/fix-windows-validation-scripts.md:

---
"fusion-skills": patch
---

Fix Windows compatibility in validation scripts

- Fix extractFrontmatter regex to handle \r\n line endings
- Fix parseFrontmatter split to normalize \r\n line endings
- Fix discoverLocalSkills regex to strip both / and \ path separators