chore: post-merge sync — plugins, audits, docs, cross-platform indexes

New skills integrated:
- engineering/behuman, code-tour, demo-video, data-quality-auditor

Plugins & marketplace:
- Add plugin.json for code-tour, demo-video, data-quality-auditor
- Add all 3 to marketplace.json (31 total plugins)
- Update marketplace counts to 248 skills, 332 tools, 460 refs

Skill fixes:
- Move data-quality-auditor from data-analysis/ to engineering/
- Fix cross-refs: code-tour, demo-video, data-quality-auditor
- Add evals.json for code-tour (5 scenarios) and demo-video (4 scenarios)
- demo-video: add output artifacts, prereqs check, references extraction
- code-tour: add default persona, parallel discovery, trivial repo guidance
- Fix Python 3.9 compat (from __future__ import annotations)

product-analytics audit fixes:
- Expand SKILL.md from 82 to 147 lines (anti-patterns, cross-refs, examples)
- Add --format json to all metrics_calculator.py subcommands
- Add error handling (FileNotFoundError, KeyError)

Docs & indexes:
- Update CLAUDE.md, README.md, docs/index.md, docs/getting-started.md counts
- Sync Codex (192 skills) and Gemini (280 items) indexes
- Regenerate MkDocs pages (279 pages, 311 HTML)
- Add 3 new nav entries to mkdocs.yml
- Update mkdocs.yml site_description

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

engineering/code-tour/.claude-plugin/plugin.json

@@ -0,0 +1,13 @@
+{
+  "name": "code-tour",
+  "description": "Create CodeTour .tour files — persona-targeted, step-by-step walkthroughs that link to real files and line numbers. Supports 10 developer personas (vibecoder, new joiner, architect, security reviewer, etc.), all CodeTour step types, and SMIG description formula.",
+  "version": "2.2.0",
+  "author": {
+    "name": "Alireza Rezvani",
+    "url": "https://alirezarezvani.com"
+  },
+  "homepage": "https://github.com/alirezarezvani/claude-skills/tree/main/engineering/code-tour",
+  "repository": "https://github.com/alirezarezvani/claude-skills",
+  "license": "MIT",
+  "skills": "./"
+}