chore: baseline snapshot before moderation-strictness feature

Repo .git was damaged (refs/ missing, index truncated, object store near-empty).
Repaired via git init (rebuilt refs), stale index preserved as .git/index.corrupt-20260910.bak,
then full worktree committed as a rollback baseline.

internal/conf/limits_test.go

@@ -0,0 +1,127 @@
+// Copyright 2026 tamakyi. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package conf
+
+import (
+	"testing"
+
+	"gopkg.in/ini.v1"
+)
+
+// TestLimitsDefaults 保证内置默认值与旧版硬编码一致：未配置 [limits] 段（或 conf.Init
+// 尚未调用）时，程序按这些默认值运行。
+func TestLimitsDefaults(t *testing.T) {
+	cases := []struct {
+		name string
+		got  int
+		want int
+	}{
+		{"MaxTags", Limits.MaxTags, 5},
+		{"MaxTagLen", Limits.MaxTagLen, 5},
+		{"MaxBlockWords", Limits.MaxBlockWords, 10},
+		{"MaxBlockWordLen", Limits.MaxBlockWordLen, 10},
+		{"CustomAnswerLen", Limits.CustomAnswerLen, 200},
+		{"VoteOptionLen", Limits.VoteOptionLen, 300},
+		{"QuestionContentLen", Limits.QuestionContentLen, 1000},
+		{"AnswerContentLen", Limits.AnswerContentLen, 2000},
+		{"FollowUpContentLen", Limits.FollowUpContentLen, 2000},
+		{"ChatMessageLen", Limits.ChatMessageLen, 2000},
+		{"ChatMaxMessages", Limits.ChatMaxMessages, 200},
+		{"DailyMessageLimitMax", Limits.DailyMessageLimitMax, 999},
+	}
+	for _, c := range cases {
+		if c.got != c.want {
+			t.Errorf("%s = %d, want %d", c.name, c.got, c.want)
+		}
+	}
+}
+
+// TestLimitsMapTo 模拟 conf.Init 的映射行为：显式键被覆盖，缺失键保留默认。
+// 启动逻辑是 File.Section("limits").MapTo(&Limits)，与这里同一路径。
+func TestLimitsMapTo(t *testing.T) {
+	src := `
+[limits]
+max_tags = 7
+chat_message_len = 500
+answer_content_len = 300
+daily_message_limit_max = 0
+`
+	f, err := ini.LoadSources(ini.LoadOptions{IgnoreInlineComment: true}, []byte(src))
+	if err != nil {
+		t.Fatalf("parse ini: %v", err)
+	}
+	l := Limits // 拷贝默认值，等价于启动前状态
+	if err := f.Section("limits").MapTo(&l); err != nil {
+		t.Fatalf("map [limits]: %v", err)
+	}
+	if l.MaxTags != 7 {
+		t.Errorf("MaxTags = %d, want 7 (ini 覆盖失败)", l.MaxTags)
+	}
+	if l.ChatMessageLen != 500 {
+		t.Errorf("ChatMessageLen = %d, want 500", l.ChatMessageLen)
+	}
+	if l.AnswerContentLen != 300 {
+		t.Errorf("AnswerContentLen = %d, want 300（ini 覆盖失败）", l.AnswerContentLen)
+	}
+	if l.DailyMessageLimitMax != 0 {
+		t.Errorf("DailyMessageLimitMax = %d, want 0（配置为 0 应生效）", l.DailyMessageLimitMax)
+	}
+	// 未显式出现的键保留内置默认
+	if l.MaxTagLen != 5 {
+		t.Errorf("MaxTagLen = %d, want 5（缺失键应保留默认）", l.MaxTagLen)
+	}
+	if l.VoteOptionLen != 300 {
+		t.Errorf("VoteOptionLen = %d, want 300", l.VoteOptionLen)
+	}
+	if l.QuestionContentLen != 1000 || l.FollowUpContentLen != 2000 {
+		t.Errorf("QuestionContentLen/FollowUpContentLen = %d/%d, want 1000/2000（缺失键应保留默认）",
+			l.QuestionContentLen, l.FollowUpContentLen)
+	}
+}
+
+// TestLimitsEmptyValueSanitized 验证「键留空」的防护：ini 会把空 int 解析为 0，
+// sanitizeLimits 随后将其回退到内置默认 —— 防止留空把上限静默置零（标签全拒等）。
+func TestLimitsEmptyValueSanitized(t *testing.T) {
+	src := `
+[limits]
+max_tags =
+chat_message_len = 0
+followup_content_len = -1
+daily_message_limit_max = -3
+`
+	f, err := ini.LoadSources(ini.LoadOptions{IgnoreInlineComment: true}, []byte(src))
+	if err != nil {
+		t.Fatalf("parse ini: %v", err)
+	}
+	l := Limits
+	if err := f.Section("limits").MapTo(&l); err != nil {
+		t.Fatalf("map [limits]: %v", err)
+	}
+	// 前提确认：空串对 int 是「保留原值」而非 0（gopkg.in/ini 行为）；
+	// 显式 0 / 负数则照常映射。真正的 0 陷阱来自显式填 0 / 负数，由 sanitize 兜底。
+	if l.MaxTags != defaultMaxTags {
+		t.Fatalf("precondition broken: 空值 max_tags 应保留默认, got %d", l.MaxTags)
+	}
+	if l.ChatMessageLen != 0 || l.DailyMessageLimitMax != -3 {
+		t.Fatalf("precondition broken: got %d/%d, want 0/-3",
+			l.ChatMessageLen, l.DailyMessageLimitMax)
+	}
+	sanitizeLimits(&l)
+	if l.MaxTags != defaultMaxTags {
+		t.Errorf("MaxTags = %d, want 默认 %d", l.MaxTags, defaultMaxTags)
+	}
+	if l.ChatMessageLen != defaultChatMessageLen {
+		t.Errorf("ChatMessageLen = %d, want 默认 %d（0 应回退默认）", l.ChatMessageLen, defaultChatMessageLen)
+	}
+	if l.FollowUpContentLen != defaultFollowUpContentLen {
+		t.Errorf("FollowUpContentLen = %d, want 默认 %d（负数应回退默认）", l.FollowUpContentLen, defaultFollowUpContentLen)
+	}
+	if l.DailyMessageLimitMax != defaultDailyMessageLimitMax {
+		t.Errorf("DailyMessageLimitMax = %d, want 默认 %d（负数应回退默认）", l.DailyMessageLimitMax, defaultDailyMessageLimitMax)
+	}
+	if l.ChatMaxMessages != defaultChatMaxMessages {
+		t.Errorf("ChatMaxMessages = %d, want 默认 %d（缺失键不受影响）", l.ChatMaxMessages, defaultChatMaxMessages)
+	}
+}