v0.3.0

Minor release. Adds the mainwp skill install subcommand and ships
the first version of the SKILL.md bundle so AI agents (Claude Code,
Codex, opencode, Pi, etc.) can pick up mainwp-cli guidance
automatically.

What's new since v0.2.1:

• mainwp skill install — install the mainwp-cli skill into one or
  more AI agents in a single command. Interactive by default with
  gum choose --no-limit (space to toggle, enter to confirm); a
  plain read prompt is the fallback when gum is missing. The
  supported agents are:
  • claude-code → ~/.claude/skills/
  • codex → ~/.codex/skills/
  • pi → ~/.pi/agent/skills/
  • opencode → ~/.config/opencode/skills/
  • global → ~/.agents/skills/
    --agent NAME (repeatable) and --all are available for
    non-interactive use.
• New skills/mainwp-cli/SKILL.md bundle (YAML frontmatter, with
  when-to-load, setup, common patterns, error handling, and API
  docs links). The bundle is at the repo root, so the Homebrew
  install ships it without any change to the formula.
• Updated bash and zsh completion scripts to cover the new
  skill install subcommand.
• Fixed a latent bug in lib/commands/deps.sh where the helper
  was being called without the eval wrapper, leaving
  REMAINING unset in the caller's scope; same fix applied
  preventively in lib/commands/skill.sh.
• 45 smoke tests passing (up from 32). The new section installs
  the skill into a sandboxed HOME and verifies SKILL.md lands
  in every agent's directory, plus the --agent and --no-input
  error paths.

The Homebrew tap updates automatically; users get the new version
with brew update && brew upgrade mainwp.