fix(i18n): 复审 r1 —— 两句近义软件渲染说明合一，生效层级码翻成译文（M180）

P2-1（一屏两句重复）：
- 留面板那一句（就在被禁用的滑块旁边，正好回答「为什么拖不动」），措辞同时点名面板与玻璃
- 删 `SettingsAppearanceSoftwareRendererNote`（catalog 一条 + 金表一行，两边同时删）
- 删 `bg_image.rs` 的 `backend_note` 渲染块与 `State::backend_note()`；state.rs 391 → 382 行

P2-2（配色：preset 的机器码）：
- `palette::level_key(code)` 把 `preset`/`wallpaper`/其余 映射到已有的三条档位 key，不新增平行词表
- `bg_image.rs` 用 `tr(PaletteLevel, {level})` 传译文，中文界面显示「配色：内置色卡」
- 补 `every_level_code_maps_to_its_own_sentence`：三个码值一一对应 + 三条译文互不相同

顺手（复审 L-1/L-2/L-4，全在本 scope 内）：
- `appearance_texts` 加「渲染后不许残留 `{`」断言（参数名写错当场红）
- `section/mod.rs` 文档：取词口 t/tr、填充措辞、清掉孤立 `//!`、把「没有一句英文」改成
  写明两处例外（`{reason}` 原文串、专名）

crates/i18n/src/catalog/golden/tail.rs

@@ -38,7 +38,7 @@ pub(super) const ROWS: &[(&str, &str, &str)] = &[
     ("SettingsAppearancePanelOpacity", "Panel transparency", "面板透明度"),
     ("SettingsAppearancePanelOpacityHint", "Only the panel/card layer. Floor {floor}; independent of window transparency.", "只作用于面板 / 卡片这一层。下限 {floor}；与整窗透明度互不影响。"),
     ("SettingsAppearancePanelOpacityForcedValue", "100% (forced from {requested})", "100%（强制，原请求值 {requested}）"),
-    ("SettingsAppearancePanelOpacityForcedHint", "Software renderer: panels stay fully opaque (window transparency still works).", "软件渲染：面板恒为不透明（整窗透明度仍然有效）。"),
+    ("SettingsAppearancePanelOpacityForcedHint", "Software renderer: panels and glass stay fully opaque (window transparency still works).", "软件渲染：面板与玻璃效果恒为不透明（整窗透明度仍然有效）。"),
     ("SettingsAppearanceBackgroundImage", "Background image", "背景图"),
     ("SettingsAppearanceOff", "Off", "关"),
     ("SettingsAppearanceOn", "On", "开"),
@@ -54,7 +54,6 @@ pub(super) const ROWS: &[(&str, &str, &str)] = &[
     ("SettingsAppearancePaletteBackground", "Background", "取自背景图"),
     ("SettingsAppearancePaletteWallpaper", "Wallpaper", "取自壁纸"),
     ("SettingsAppearancePalettePreset", "Preset", "内置色卡"),
-    ("SettingsAppearanceSoftwareRendererNote", "Software renderer: panel transparency and glass stay fully opaque (window transparency still works).", "软件渲染：面板透明度与玻璃效果恒为不透明（整窗透明度仍然有效）。"),
     ("SettingsAppearanceBgReadFailed", "Background image could not be read: {reason}", "背景图读不出来：{reason}"),
     ("SettingsAppearanceBgDecodeFailed", "Background image could not be decoded ({reason}; this build decodes PNG, JPEG and BMP)", "背景图解不开（{reason}；这个构建只支持 PNG、JPEG 与 BMP）"),
     ("SettingsAppearanceBgTooLarge", "Background image is too large to decode: {width}×{height} (limit {limit} px per edge)", "背景图太大，解不开：{width}×{height}（每边上限 {limit} 像素）"),

crates/i18n/src/catalog/settings/appearance.rs

@@ -70,8 +70,8 @@ macro_rules! settings_appearance_entries {
                 "100%（强制，原请求值 {requested}）"
             ),
             SettingsAppearancePanelOpacityForcedHint => (
-                "Software renderer: panels stay fully opaque (window transparency still works).",
-                "软件渲染：面板恒为不透明（整窗透明度仍然有效）。"
+                "Software renderer: panels and glass stay fully opaque (window transparency still works).",
+                "软件渲染：面板与玻璃效果恒为不透明（整窗透明度仍然有效）。"
             ),
             SettingsAppearanceBackgroundImage => ("Background image", "背景图"),
             SettingsAppearanceOff => ("Off", "关"),
@@ -91,11 +91,10 @@ macro_rules! settings_appearance_entries {
             SettingsAppearancePaletteBackground => ("Background", "取自背景图"),
             SettingsAppearancePaletteWallpaper => ("Wallpaper", "取自壁纸"),
             SettingsAppearancePalettePreset => ("Preset", "内置色卡"),
-            // ---- M180：运行时诊断（`state.rs` 的 backend_note + `background.rs` 的三种读盘失败 + 小图平铺）
-            SettingsAppearanceSoftwareRendererNote => (
-                "Software renderer: panel transparency and glass stay fully opaque (window transparency still works).",
-                "软件渲染：面板透明度与玻璃效果恒为不透明（整窗透明度仍然有效）。"
-            ),
+            // ---- M180：运行时诊断（`background.rs` 的三种读盘失败 + 小图平铺）。
+            //
+            // M180 r1 复审 P2-1：软件渲染那句**只有一条**，就挂在面板那一行（`PanelOpacityForcedHint`）
+            // 上——它挨着被禁用的滑块，正好回答「为什么拖不动」；这里不再有第二句。
             SettingsAppearanceBgReadFailed => (
                 "Background image could not be read: {reason}",
                 "背景图读不出来：{reason}"