feat(commands): add /plugin-audit — 8-phase validation pipeline for skills and plugins

- Add commands/plugin-audit.md (distributable) + .claude/commands/plugin-audit.md (local invocation)
- 8 phases: discovery, structure validation, quality scoring, script testing,
  security audit, marketplace compliance, ecosystem integration, domain code review
- Auto-fixes non-critical issues, only prompts user for breaking changes
- Integrates skill_validator.py, quality_scorer.py, script_tester.py, skill_security_auditor.py
- Domain-appropriate review via cs-* agents (engineering, product, marketing, etc.)
- Update product-team counts: 12→14 skills, 13→16 tools, 7→8 commands
- Add /code-to-prd and /plugin-audit to mkdocs.yml nav
- Regenerate docs (248 pages, 19 commands)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.claude-plugin/marketplace.json

@@ -129,7 +129,7 @@
     {
       "name": "product-skills",
       "source": "./product-team",
-      "description": "13 product skills with 13 Python tools: product manager toolkit (RICE, PRDs), agile product owner, product strategist, UX researcher, UI design system, competitive teardown, landing page generator, SaaS scaffolder, product analytics, experiment designer, product discovery, roadmap communicator.",
+      "description": "14 product skills with 16 Python tools: product manager toolkit (RICE, PRDs), agile product owner, product strategist, UX researcher, UI design system, competitive teardown, landing page generator, SaaS scaffolder, product analytics, experiment designer, product discovery, roadmap communicator, code-to-prd, research summarizer.",
       "version": "2.1.2",
       "author": {
         "name": "Alireza Rezvani"