Skills repo cleanup — fix naming inconsistency and align with registry

[theuseless-ai]

Overview

The existing theuselessai/skills repo has naming inconsistencies and needs alignment with the new registry-based distribution model.

Issues

1. skills.json references wrong repo name: "repository": "theuselessai/useless-skills" but the actual repo is theuselessai/skills
2. README clone URL wrong: References theuselessai/useless-skills.git
3. Description outdated: "Skills Registry / Repository for Pipelit" → should reference plit ecosystem
4. skills.json will be superseded by theuselessai/registry — but can coexist during transition

Tasks

• Fix skills.json repository field to theuselessai/skills
• Fix README clone/fork URLs
• Update repo description to reference plit ecosystem
• Update README branding (Pipelit → plit ecosystem)
• Set up per-package tagging convention (dev-plan/v1.0.2)
• Add CI to package individual skills as release assets on tag
• Add CI to update theuselessai/registry on tag

Notes

• Existing skills.json can remain as a local manifest during transition
• Full registry integration happens when Create theuselessai/registry — unified package index #60 (registry repo) lands