Add PR Description, Self-Review, and Repo Orientation skills

[Hazey000]

Summary

Add three new workflow skills for daily SE quality-of-life: drafting PR descriptions from local git history, self-reviewing diffs against the existing reviewer checklists, and generating repo orientation/onboarding guides. All three are filesystem/git-only with zero external dependencies. Also adds .DS_Store and .vscode to .gitignore.

Changes

• pr-description/SKILL.md — new skill that gathers branch context via git, detects a repo PR template if present, infers linked tickets from branch/commit names, and drafts a title + body. Optionally creates the PR via gh pr create.
• self-review/SKILL.md — new skill that auto-discovers installed reviewers/review-*/SKILL.md via glob, routes changed files to applicable reviewers based on path/content patterns, and produces a consolidated CRITICAL/WARNING/SUGGESTION report.
• repo-orientation/SKILL.md — new skill that detects the tech stack, maps directory structure, finds entry points, and summarises conventions/CI into an onboarding guide. Works on any language/stack via heuristic detection.
• README.md — added usage documentation for all three new skills.
• .gitignore — added .DS_Store and .vscode/ to prevent IDE/OS artifacts from being tracked.

Test Plan

• Manual verification: installed all three skills and ran each one in a Cursor session to confirm they trigger correctly and produce expected output
• Verified self-review's glob discovery finds all 8 existing reviewers in reviewers/
• Confirmed README entries match the format of existing skill entries