fix(ai): Ask P0 禁 CoT、可澄清、禁 UPDATE_TIME 终答

prompt 禁止推理外露与编造列；信息不足允许一句澄清。
新增 SanitizeAssistantContent 剥回复中的推理草稿；业务「最近 N 天」不得默认用 information_schema.UPDATE_TIME。

server/internal/ai/sanitize.go

@@ -0,0 +1,111 @@
+package ai
+
+import (
+	"regexp"
+	"strings"
+	"unicode/utf8"
+)
+
+var (
+	anyFence     = regexp.MustCompile("(?s)```[a-zA-Z]*\\s*\n.*?```")
+	cotCue       = regexp.MustCompile(`(?i)(我们需要|作为助手|指令要求|让我们看看|最终答案|chain of thought|step by step|I need to|as an assistant|the instruction)`)
+	sqlFenceFind = regexp.MustCompile("(?s)```sql\\s*\n(.+?)```")
+)
+
+// SanitizeAssistantContent 去掉 Ask/Generate 回复里的推理草稿，只保留短说明 + SQL 块（或短澄清）。
+func SanitizeAssistantContent(content string) string {
+	s := strings.TrimSpace(content)
+	if s == "" {
+		return s
+	}
+	fences := anyFence.FindAllStringIndex(s, -1)
+	if len(fences) == 0 {
+		if utf8.RuneCountInString(s) <= 240 && !cotCue.MatchString(s) {
+			return s
+		}
+		return keepLeadingLines(s, 2)
+	}
+	var b strings.Builder
+	prev := 0
+	for i, loc := range fences {
+		prose := strings.TrimSpace(s[prev:loc[0]])
+		if prose != "" {
+			if i == 0 {
+				prose = trimProse(prose)
+			} else {
+				prose = keepLeadingLines(prose, 2)
+			}
+			if prose != "" {
+				if b.Len() > 0 {
+					b.WriteByte('\n')
+				}
+				b.WriteString(prose)
+			}
+		}
+		if b.Len() > 0 {
+			b.WriteString("\n\n")
+		}
+		b.WriteString(strings.TrimSpace(s[loc[0]:loc[1]]))
+		prev = loc[1]
+	}
+	tail := strings.TrimSpace(s[prev:])
+	if tail != "" {
+		tail = keepLeadingLines(tail, 2)
+		if tail != "" {
+			b.WriteString("\n\n")
+			b.WriteString(tail)
+		}
+	}
+	out := strings.TrimSpace(b.String())
+	if out == "" {
+		if m := sqlFenceFind.FindString(s); m != "" {
+			return strings.TrimSpace(m)
+		}
+		return keepLeadingLines(s, 2)
+	}
+	return out
+}
+
+func trimProse(prose string) string {
+	lines := nonEmptyLines(prose)
+	if len(lines) == 0 {
+		return ""
+	}
+	var notes []string
+	for _, ln := range lines {
+		if strings.HasPrefix(ln, "说明") || strings.HasPrefix(ln, "注意") || strings.HasPrefix(ln, "提示") {
+			notes = append(notes, ln)
+		}
+	}
+	if len(notes) > 0 {
+		if len(notes) > 2 {
+			notes = notes[len(notes)-2:]
+		}
+		return strings.Join(notes, "\n")
+	}
+	joined := strings.Join(lines, "\n")
+	if cotCue.MatchString(joined) || utf8.RuneCountInString(joined) > 160 {
+		return ""
+	}
+	return keepLeadingLines(joined, 2)
+}
+
+func keepLeadingLines(s string, n int) string {
+	lines := nonEmptyLines(s)
+	if len(lines) > n {
+		lines = lines[:n]
+	}
+	return strings.Join(lines, "\n")
+}
+
+func nonEmptyLines(s string) []string {
+	raw := strings.Split(s, "\n")
+	out := make([]string, 0, len(raw))
+	for _, ln := range raw {
+		ln = strings.TrimSpace(ln)
+		if ln != "" {
+			out = append(out, ln)
+		}
+	}
+	return out
+}