Package agent skills as a portable agent plugin

[gtsiolis]

Motivation

PRO-373 tracks the first distribution step for making the LocalStack skills repository portable across agent clients. The repository already exposed Claude-specific metadata, but it did not provide the standard root manifest and package structure expected by Agent Plugin clients.

Solution

• add an Agent Plugins v1.0.0 plugin.json manifest
• align skill directories with their public Agent Skill names
• update all six skills to use current lstk v2 workflows and clearly mark unsupported boundaries
• document portable plugin, Agent Skills CLI, and existing Claude Code installation paths
• add pinned local and CI validation for the plugin manifest and every skill
• keep this first step skills-only, without introducing an MCP manifest

Docs

Documentation impact

The repository README now documents the portable package layout, supported installation paths, prerequisites, and validation workflow. No separate documentation update is needed.

Validation

• ./scripts/validate.sh
• claude plugin validate --strict .
• shellcheck scripts/validate.sh
• bash -n scripts/validate.sh
• JSON and workflow YAML parsing
• git diff --cached --check

Review

Human review is advised because this changes package discovery paths and rewrites all six user-facing skills.

Closes PRO-373

Closes PRO-194