fix(plugin): slim Claude Code install (291MB→770KB) + fix skills path

- Marketplace source moved from "./" to "./plugin", a thin generated
  subtree containing only the plugin manifest and the impeccable skill.
  Per-version plugin cache shrinks ~378× (~770 KB instead of ~291 MB),
  and the lockfile is no longer included in the source path so the
  cache extraction never runs bun install. (#107)
- skills field in plugin.json now ends with a trailing slash to match
  the documented schema (code.claude.com/docs/en/plugins-reference,
  every directory example uses ./path/). Three reporters converged on
  this fix because Claude Code's plugin loader skips command
  registration on some setups when the slash is missing. (#86)
- Anti-patterns maintenance agent moved out of .claude/agents/ into
  CLAUDE.md / AGENTS.md as concise inline guidance, since it is
  repo-internal dev workflow, not user-facing. The plugin was also
  the only place this agent was exposed to install users.
- Skills version bumped to 3.0.2 so existing users pick up the new
  install path on next /plugin update.
- Top-level harness directories (.claude/skills/, .cursor/skills/, ...)
  intentionally stay where they are; npx skills add reads them
  directly from the GitHub repo and that path is unaffected.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.opencode/skills/impeccable/SKILL.md

@@ -1,7 +1,7 @@
 ---
 name: impeccable
 description: Use when the user wants to design, redesign, shape, critique, audit, polish, clarify, distill, harden, optimize, adapt, animate, colorize, extract, or otherwise improve a frontend interface. Covers websites, landing pages, dashboards, product UI, app shells, components, forms, settings, onboarding, and empty states. Handles UX review, visual hierarchy, information architecture, cognitive load, accessibility, performance, responsive behavior, theming, anti-patterns, typography, fonts, spacing, layout, alignment, color, motion, micro-interactions, UX copy, error states, edge cases, i18n, and reusable design systems or tokens. Also use for bland designs that need to become bolder or more delightful, loud designs that should become quieter, live browser iteration on UI elements, or ambitious visual effects that should feel technically extraordinary. Not for backend-only or non-UI tasks.
-version: 3.0.1
+version: 3.0.2
 user-invocable: true
 argument-hint: "[craft|shape · audit|critique · animate|bolder|colorize|delight|layout|overdrive|quieter|typeset · adapt|clarify|distill · harden|onboard|optimize|polish · teach|document|extract|live] [target]"
 license: Apache 2.0. Based on Anthropic's frontend-design skill. See NOTICE.md for attribution.