feat: add repo-hygiene skill for periodic repository health checks

New maintenance/repo-hygiene skill covering 8 categories (~45 checks):
dependencies, git, CI/CD, code quality, docs, config, security, metadata.
Supports Node/TS, Python, and Go. Includes baseline tracking, auto-fix
offers with tiered safety, and scoring system.

Co-Authored-By: Pi <noreply@pi.dev>

Author: marcfargas

README.md

@@ -7,6 +7,7 @@ Reusable skills for AI coding agents. Works with [pi](https://github.com/marioze
 | Category | Skill | Description |
 |----------|-------|-------------|
 | ☁️ Google Cloud | [gcloud](google-cloud/gcloud/) | GCP CLI with agent safety model — hub + 7 reference files |
+| 🔧 Maintenance | [repo-hygiene](maintenance/repo-hygiene/) | Periodic repo health check — deps, git, CI, code quality, docs, security |
 | ⚙️ Process | [pm2](process/pm2/) | Process management — keep services alive, auto-restart, monitoring, ecosystem configs |
 | 🚀 Release | [pre-release](release/pre-release/) | Pre-release checklist + AI-written changesets via @changesets/cli |
 | 🔍 Search | [web-search](search/web-search/) | Web search + content extraction via [ddgs](https://github.com/deedy5/ddgs) — no API keys |
@@ -71,6 +72,8 @@ Skills use a **hub + spoke** architecture. The SKILL.md hub is ~140 lines — ju
 skills/
 ├── google-cloud/
 │   └── gcloud/          # 8 files, ~1100 lines total
+├── maintenance/
+│   └── repo-hygiene/    # 1 file — periodic health check
 ├── process/
 │   └── pm2/             # 1 file
 ├── release/