docs,ci: P2 质量体系 — 技术债看板 + 冻结策略 + fix 率趋势

- 新增 fix-rate-trend.sh: 按周统计 fix 率趋势 + 类别分布
  当前: 22.8% (177/776), 目标 < 15%
- 新增 docs/tech-debt-board.md: 技术债看板
  含度量总览、高利息债务排序、已偿还债务、偿还优先级
- 新增 docs/discussions/2026-05-13-frozen-module-strategy.md:
  6 个冻结模块策略 + 14 天超时规则 + 解冻/移除操作流程

scripts/fix-rate-trend.sh

@@ -0,0 +1,120 @@
+#!/usr/bin/env bash
+# fix-rate-trend.sh — Fix 率趋势监控
+#
+# 分析 git 提交历史，按周统计 fix 率趋势。
+# Fix 定义: 提交消息以 "fix" 开头（conventional commits）。
+#
+# 用法:
+#   bash scripts/fix-rate-trend.sh           # 全量趋势
+#   bash scripts/fix-rate-trend.sh 30        # 最近 30 天
+#
+# 目标: fix 率 < 15%（当前 ~23%）
+
+set -uo pipefail
+cd "$(git rev-parse --show-toplevel)"
+
+DAYS="${1:-999}"
+SINCE=""
+if [ "$DAYS" != "999" ]; then
+  SINCE="--since=\"${DAYS} days ago\""
+fi
+
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+NC='\033[0m'
+
+echo "=========================================="
+echo "  Fix Rate Trend — fix / total commits"
+if [ "$DAYS" != "999" ]; then
+  echo "  (Last ${DAYS} days)"
+fi
+echo "=========================================="
+echo ""
+
+# Collect weekly stats
+declare -a WEEKS=()
+declare -a TOTALS=()
+declare -a FIXES=()
+declare -a RATES=()
+
+eval "git log --oneline --format='%ad|%s' --date=short $SINCE" | while IFS='|' read -r date msg; do
+  echo "$date|$msg"
+done | awk -F'|' '
+{
+  date = $1
+  msg = $2
+  # Get ISO week number (year-week)
+  cmd = "date -d \"" date "\" +\"%G-W%V\" 2>/dev/null || date -j -f \"%Y-%m-%d\" \"" date "\" +\"%G-W%V\" 2>/dev/null"
+  cmd | getline week
+  close(cmd)
+
+  total[week]++
+  if (msg ~ /^fix[\(:]/ || msg ~ /^fix$/) {
+    fix[week]++
+  } else {
+    fix[week] += 0
+  }
+}
+END {
+  n = asorti(total, sorted)
+  for (i = 1; i <= n; i++) {
+    w = sorted[i]
+    f = fix[w] + 0
+    t = total[w]
+    r = (f / t) * 100
+    printf "%s|%d|%d|%.1f\n", w, t, f, r
+  }
+}' > /tmp/fix-rate-$$.tmp
+
+# Display results
+printf "%-12s %6s %6s %8s  %s\n" "WEEK" "TOTAL" "FIX" "RATE" "BAR"
+echo "------------------------------------------------------------"
+
+ALL_TOTAL=0
+ALL_FIX=0
+
+while IFS='|' read -r week total fix rate; do
+  ALL_TOTAL=$((ALL_TOTAL + total))
+  ALL_FIX=$((ALL_FIX + fix))
+
+  # Color code by rate
+  bar_len=$(echo "$rate" | awk '{printf "%d", $1 / 5}')
+  bar=""
+  for ((i=0; i<bar_len; i++)); do bar="${bar}#"; done
+
+  if awk "BEGIN { exit ($rate < 15) ? 1 : 0 }"; then
+    if awk "BEGIN { exit ($rate < 25) ? 1 : 0 }"; then
+      color=$YELLOW
+    else
+      color=$RED
+    fi
+  else
+    color=$GREEN
+  fi
+
+  printf "%-12s %6d %6d " "$week" "$total" "$fix"
+  echo -e "${color}${rate}%${NC}  ${bar}"
+done < /tmp/fix-rate-$$.tmp
+
+rm -f /tmp/fix-rate-$$.tmp
+
+echo "------------------------------------------------------------"
+ALL_RATE=$(awk "BEGIN { printf \"%.1f\", ($ALL_FIX / $ALL_TOTAL) * 100 }")
+echo ""
+echo -e "Total: ${ALL_TOTAL} commits, ${ALL_FIX} fixes, rate: ${ALL_RATE}%"
+echo ""
+
+# Category breakdown for the most recent period
+echo "=========================================="
+echo "  Fix Category Breakdown (recent)"
+echo "=========================================="
+
+eval "git log --oneline --format='%s' $SINCE" | grep -iE "^fix" | \
+  sed -E 's/^fix\([^)]*\):? ?//' | \
+  grep -oE '(permission|auth|安全|security|tenant|CORS|SQL|XSS|前端|后端|接口|字段|API|路由|route|menu|菜单|编译|compile|类型|type|migration|迁移|race|竞态|token|event|事件|login|登录|miniprogram|小程序|Taro|media|轮播|banner)' | \
+  sort | uniq -c | sort -rn | head -15
+
+echo ""
+echo "Target: fix rate < 15%"
+echo "Red line: fix rate > 20% triggers review (see CLAUDE.md)"