生成图片的允许值与边界提成常量，校验与诊断文案共用同一份

- 新增 GENERATE_IMAGE_ASPECT_RATIOS / _IMAGE_SIZES / _SLICE_MODES 与 grid 轴、sliceCount 的 MIN/MAX 常量，放在 direct_tool_bridge 的 GENERATE_IMAGE_ARGUMENTS 旁
- generate_image_input 的 aspectRatio / imageSize / sliceMode / grid 轴区间 / sliceCount 区间校验改为读常量；generate_image/error.rs 的对应文案也改为读同一批常量（KindUnsupported 早已从 PLATFORM_ART_ASSET_GENERATION_KINDS 派生，这次把其余几组对齐）
- 只改取值来源，判定范围与文案取值不变
- 未纳入本次：commands.rs 的 LOCAL_PROJECT_ASSET_ASPECT_RATIOS/_IMAGE_SIZES 与 agent_native_tools.rs 的 canvas.asset_generate schema 仍是各自的副本（面向非 agent 的栏目画布入口），统一它们属于另一次改动

验证：cargo test --bin genarrative-ai-game-creator-shell -- agent::direct_tool_bridge:: agent::direct_tools_mcp:: 71 passed

apps/ai-game-creator-shell/src-tauri/src/agent/direct_tool_bridge.rs

@@ -2711,6 +2711,17 @@ async fn bridge_prepare_game_art(
     Ok(result)
 }
 
+/// `agc_generate_image` 的受支持取值与边界：解析校验与失败文案共用同一份，
+/// 避免两边各写一遍、改动时静默漂移。
+pub(in crate::agent) const GENERATE_IMAGE_ASPECT_RATIOS: &[&str] =
+    &["1:1", "2:3", "3:2", "9:16", "16:9"];
+pub(in crate::agent) const GENERATE_IMAGE_IMAGE_SIZES: &[&str] = &["0.5K", "1K", "2K"];
+pub(in crate::agent) const GENERATE_IMAGE_SLICE_MODES: &[&str] = &["connected-components", "grid"];
+pub(in crate::agent) const GENERATE_IMAGE_GRID_AXIS_MIN: u32 = 1;
+pub(in crate::agent) const GENERATE_IMAGE_GRID_AXIS_MAX: u32 = 32;
+pub(in crate::agent) const GENERATE_IMAGE_SLICE_COUNT_MIN: u64 = 1;
+pub(in crate::agent) const GENERATE_IMAGE_SLICE_COUNT_MAX: u64 = 256;
+
 /// `agc_generate_image` 允许的入参字段。
 const GENERATE_IMAGE_ARGUMENTS: &[&str] = &[
     "prompt",
@@ -2962,15 +2973,12 @@ pub(in crate::agent) fn generate_image_input(
     let aspect_ratio =
         generate_image_optional_text(arguments, GenerateImageTextField::AspectRatio)?
             .unwrap_or_else(|| "1:1".to_string());
-    if !matches!(
-        aspect_ratio.as_str(),
-        "1:1" | "2:3" | "3:2" | "9:16" | "16:9"
-    ) {
+    if !GENERATE_IMAGE_ASPECT_RATIOS.contains(&aspect_ratio.as_str()) {
         return Err(GenerateImageError::AspectRatioUnsupported { got: aspect_ratio });
     }
     let image_size = generate_image_optional_text(arguments, GenerateImageTextField::ImageSize)?
         .unwrap_or_else(|| "1K".to_string());
-    if !matches!(image_size.as_str(), "0.5K" | "1K" | "2K") {
+    if !GENERATE_IMAGE_IMAGE_SIZES.contains(&image_size.as_str()) {
         return Err(GenerateImageError::ImageSizeUnsupported { got: image_size });
     }
     let asset_name = generate_image_optional_text(arguments, GenerateImageTextField::AssetName)?
@@ -2979,7 +2987,7 @@ pub(in crate::agent) fn generate_image_input(
     let slice_mode = generate_image_optional_text(arguments, GenerateImageTextField::SliceMode)?;
     if slice_mode
         .as_deref()
-        .is_some_and(|mode| !matches!(mode, "connected-components" | "grid"))
+        .is_some_and(|mode| !GENERATE_IMAGE_SLICE_MODES.contains(&mode))
     {
         return Err(GenerateImageError::SliceModeUnsupported {
             got: slice_mode.unwrap_or_default(),
@@ -2991,7 +2999,9 @@ pub(in crate::agent) fn generate_image_input(
         return Err(GenerateImageError::GridAxesMissing);
     }
     for (axis, value) in [("gridX", grid_x), ("gridY", grid_y)] {
-        if let Some(got) = value.filter(|value| !(1..=32).contains(value)) {
+        if let Some(got) = value.filter(|value| {
+            !(GENERATE_IMAGE_GRID_AXIS_MIN..=GENERATE_IMAGE_GRID_AXIS_MAX).contains(value)
+        }) {
             return Err(GenerateImageError::GridOutOfRange { axis, got });
         }
     }
@@ -3001,7 +3011,10 @@ pub(in crate::agent) fn generate_image_input(
         .map(|value| {
             value
                 .as_u64()
-                .filter(|count| (1..=256).contains(count))
+                .filter(|count| {
+                    (GENERATE_IMAGE_SLICE_COUNT_MIN..=GENERATE_IMAGE_SLICE_COUNT_MAX)
+                        .contains(count)
+                })
                 .map(|count| count as usize)
                 .ok_or_else(|| GenerateImageError::SliceCountInvalid {
                     got: value.to_string(),

apps/ai-game-creator-shell/src-tauri/src/agent/tool/generate_image/error.rs

@@ -2,6 +2,11 @@
 //!
 //! 这里只放错误本身；参数解析与工具执行留在 `direct_tool_bridge`。
 
+use crate::agent::direct_tool_bridge::{
+    GENERATE_IMAGE_ASPECT_RATIOS, GENERATE_IMAGE_GRID_AXIS_MAX, GENERATE_IMAGE_GRID_AXIS_MIN,
+    GENERATE_IMAGE_IMAGE_SIZES, GENERATE_IMAGE_SLICE_COUNT_MAX, GENERATE_IMAGE_SLICE_COUNT_MIN,
+    GENERATE_IMAGE_SLICE_MODES,
+};
 use crate::agent::generation::PLATFORM_ART_ASSET_GENERATION_KINDS;
 use crate::agent::tool::error::{ProjectPermissionRejection, ToolArgumentsRejection, ToolFailure};
 use shared_contracts::game_creation_app::GameCreationAppAssetKind;
@@ -84,7 +89,8 @@ impl ToolFailure for GenerateImageError {
                 "生成图片失败：aspectRatio 含有控制字符。".to_string()
             }
             Self::AspectRatioUnsupported { got } => format!(
-                "生成图片失败：aspectRatio「{got}」不是受支持的比例，只能是 1:1、2:3、3:2、9:16、16:9。"
+                "生成图片失败：aspectRatio「{got}」不是受支持的比例，只能是 {}。",
+                GENERATE_IMAGE_ASPECT_RATIOS.join("、")
             ),
             Self::ImageSizeEmpty => "生成图片失败：imageSize 传了空值。".to_string(),
             Self::ImageSizeTooLong {
@@ -95,7 +101,8 @@ impl ToolFailure for GenerateImageError {
                 "生成图片失败：imageSize 含有控制字符。".to_string()
             }
             Self::ImageSizeUnsupported { got } => format!(
-                "生成图片失败：imageSize「{got}」不是受支持的图片尺寸，只能是 0.5K、1K、2K。"
+                "生成图片失败：imageSize「{got}」不是受支持的图片尺寸，只能是 {}。",
+                GENERATE_IMAGE_IMAGE_SIZES.join("、")
             ),
             Self::AssetNameEmpty => "生成图片失败：assetName 传了空值。".to_string(),
             Self::AssetNameTooLong {
@@ -122,7 +129,8 @@ impl ToolFailure for GenerateImageError {
                 "生成图片失败：sliceMode 含有控制字符。".to_string()
             }
             Self::SliceModeUnsupported { got } => format!(
-                "生成图片失败：sliceMode「{got}」不受支持，只允许 connected-components 或 grid。"
+                "生成图片失败：sliceMode「{got}」不受支持，只允许 {}。",
+                GENERATE_IMAGE_SLICE_MODES.join("、")
             ),
             Self::GridAxisNotInteger { axis } => {
                 format!("生成图片失败：{axis} 必须是整数。")
@@ -131,10 +139,14 @@ impl ToolFailure for GenerateImageError {
                 "生成图片失败：sliceMode=grid 必须同时提供 gridX 与 gridY。".to_string()
             }
             Self::GridOutOfRange { axis, got } => {
-                format!("生成图片失败：{axis}={got} 超出范围，gridX/gridY 必须在 1 到 32 之间。")
+                format!(
+                    "生成图片失败：{axis}={got} 超出范围，gridX/gridY 必须在 {GENERATE_IMAGE_GRID_AXIS_MIN} 到 {GENERATE_IMAGE_GRID_AXIS_MAX} 之间。"
+                )
             }
             Self::SliceCountInvalid { got } => {
-                format!("生成图片失败：sliceCount「{got}」非法，必须是 1 到 256 的整数。")
+                format!(
+                    "生成图片失败：sliceCount「{got}」非法，必须是 {GENERATE_IMAGE_SLICE_COUNT_MIN} 到 {GENERATE_IMAGE_SLICE_COUNT_MAX} 的整数。"
+                )
             }
             Self::SpritesheetSliceModeMissing => format!(
                 "生成图片失败：kind={} 必须显式声明 sliceMode，没有默认值：需求要求等分网格、固定槽位或指定行列数时传 sliceMode=grid 并提供 gridX/gridY；自由排布、数量不定或只要求一张图集时传 sliceMode=connected-components。",