chore: archive self-authored PR gate skill and cleanup

[mpaulosky]

Archive and document the self-authored PR gate skill discovered during PR #336 gate review (where GitHub blocks self-approval on PRs authored by reviewers).

Work

• Create .squad/skills/self-authored-pr-gate/SKILL.md with documented workflow
• Update Aragorn history with PR Upgrade Aspire and markdown package versions #336 gate review findings
• Verify no orphaned branches remain

Context

PR #336 (Boromir's Aspire/markdown upgrade) was self-authored with Aragorn as lead reviewer. GitHub's 422: Can not approve your own pull request required a gate pattern using CI/Copilot/Codecov checks instead of self-approval.

[github-actions]

🔄 Ralph — Auto-Triage

Assigned to: Legolas
Reason: Matched frontend/UI role keywords
Source: role-keyword

Ralph auto-triaged this issue using routing rules.
To reassign, swap the squad:* label.

[github-actions]

🏗️ Squad Triage — Aragorn (Lead / Architect)

Issue: #337 — chore: archive self-authored PR gate skill and cleanup
Assigned to: Sam (Backend / .NET)
Reason: Issue relates to backend/API work

Team roster:

• Aragorn (Lead / Architect) → label: squad:aragorn
• Sam (Backend / .NET) → label: squad:sam
• Legolas (Frontend / Blazor) → label: squad:legolas
• Gimli (Tester) → label: squad:gimli
• Boromir (DevOps / Infra) → label: squad:boromir
• Gandalf (Security / Auth) → label: squad:gandalf
• Frodo (Tech Writer) → label: squad:frodo
• Pippin (Docs) → label: squad:pippin
• Bilbo (Tech Blogger) → label: squad:bilbo
• Ralph (Meta) → label: squad:ralph

To reassign, remove the current squad:* label and add the correct one.