docs: complete documentation overhaul with v3.1.0 release notes and zh-CN translations

Documentation restructure:
- New docs/getting-started/ guide (4 files: install, quick-start, first-skill, next-steps)
- New docs/user-guide/ section (6 files: core concepts through troubleshooting)
- New docs/reference/ section (CLI_REFERENCE, CONFIG_FORMAT, ENVIRONMENT_VARIABLES, MCP_REFERENCE)
- New docs/advanced/ section (custom-workflows, mcp-server, multi-source)
- New docs/ARCHITECTURE.md - system architecture overview
- Archived legacy files (QUICKSTART.md, QUICK_REFERENCE.md, docs/guides/USAGE.md) to docs/archive/legacy/

Chinese (zh-CN) translations:
- Full zh-CN mirror of all user-facing docs (getting-started, user-guide, reference, advanced)
- GitHub Actions workflow for translation sync (.github/workflows/translate-docs.yml)
- Translation sync checker script (scripts/check_translation_sync.sh)
- Translation helper script (scripts/translate_doc.py)

Content updates:
- CHANGELOG.md: [Unreleased] → [3.1.0] - 2026-02-22
- README.md: updated with new doc structure links
- AGENTS.md: updated agent documentation
- docs/features/UNIFIED_SCRAPING.md: updated for unified scraper workflow JSON config

Analysis/planning artifacts (kept for reference):
- DOCUMENTATION_OVERHAUL_PLAN.md, DOCUMENTATION_OVERHAUL_SUMMARY.md
- FEATURE_GAP_ANALYSIS.md, IMPLEMENTATION_GAPS_ANALYSIS.md, CREATE_COMMAND_COVERAGE_ANALYSIS.md
- CHINESE_TRANSLATION_IMPLEMENTATION_SUMMARY.md, ISSUE_260_UPDATE.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/check_translation_sync.sh

@@ -0,0 +1,63 @@
+#!/bin/bash
+# Check if Chinese translations are in sync with English originals
+# Usage: ./scripts/check_translation_sync.sh
+
+set -e
+
+echo "🔍 Checking translation sync..."
+echo ""
+
+MISSING=0
+OUT_OF_SYNC=0
+
+# Find all English docs (excluding zh-CN and archive)
+find docs -name "*.md" -not -path "docs/zh-CN/*" -not -path "docs/archive/*" | while read -r en_file; do
+    # Calculate corresponding Chinese file path
+    rel_path="${en_file#docs/}"
+    zh_file="docs/zh-CN/$rel_path"
+    
+    # Check if Chinese version exists
+    if [ ! -f "$zh_file" ]; then
+        echo "❌ Missing: $zh_file (source: $en_file)"
+        MISSING=$((MISSING + 1))
+        continue
+    fi
+    
+    # Get last modification times
+    en_mtime=$(git log -1 --format=%ct "$en_file" 2>/dev/null || stat -c %Y "$en_file" 2>/dev/null || echo 0)
+    zh_mtime=$(git log -1 --format=%ct "$zh_file" 2>/dev/null || stat -c %Y "$zh_file" 2>/dev/null || echo 0)
+    
+    # Check if English is newer
+    if [ "$en_mtime" -gt "$zh_mtime" ]; then
+        echo "⚠️  Out of sync: $zh_file (English updated more recently)"
+        OUT_OF_SYNC=$((OUT_OF_SYNC + 1))
+    fi
+done
+
+echo ""
+
+# Summary
+TOTAL_EN=$(find docs -name "*.md" -not -path "docs/zh-CN/*" -not -path "docs/archive/*" | wc -l)
+TOTAL_ZH=$(find docs/zh-CN -name "*.md" 2>/dev/null | wc -l)
+
+echo "📊 Summary:"
+echo "   English docs: $TOTAL_EN"
+echo "   Chinese docs: $TOTAL_ZH"
+
+if [ "$MISSING" -gt 0 ]; then
+    echo "   ❌ Missing translations: $MISSING"
+fi
+
+if [ "$OUT_OF_SYNC" -gt 0 ]; then
+    echo "   ⚠️  Out of sync: $OUT_OF_SYNC"
+fi
+
+if [ "$MISSING" -eq 0 ] && [ "$OUT_OF_SYNC" -eq 0 ]; then
+    echo ""
+    echo "✅ All translations in sync!"
+    exit 0
+else
+    echo ""
+    echo "❌ Translation sync issues found"
+    exit 1
+fi