refactor(models): migrate to granular model configuration architecture

Upgrade Claude model configuration from dual-key to quad-key system for
better model tier differentiation.

**Breaking Changes:**
- Replace `ANTHROPIC_SMALL_FAST_MODEL` with three granular keys:
  - `ANTHROPIC_DEFAULT_HAIKU_MODEL`
  - `ANTHROPIC_DEFAULT_SONNET_MODEL`
  - `ANTHROPIC_DEFAULT_OPUS_MODEL`

**Backend (Rust):**
- Add `normalize_claude_models_in_value()` for automatic migration
- Implement fallback chain: `DEFAULT_* || SMALL_FAST || MODEL`
- Auto-cleanup: remove legacy `SMALL_FAST` key after normalization
- Apply normalization across 6 critical paths:
  - Add/update provider
  - Read from live config
  - Write to live config
  - Refresh config snapshot

**Frontend (React):**
- Expand UI from 2 to 4 model input fields
- Implement smart fallback in `useModelState` hook
- Update `useKimiModelSelector` for Kimi model picker
- Add i18n keys for Haiku/Sonnet/Opus labels (zh/en)

**Configuration:**
- Update all 7 provider presets to new format
- DeepSeek/Qwen/Moonshot: use same model for all tiers
- Zhipu: preserve tier differentiation (glm-4.5-air for Haiku)

**Backward Compatibility:**
- Old configs auto-upgrade on first read/write
- Fallback chain ensures graceful degradation
- No manual migration required

Closes #[issue-number]

src/components/providers/forms/hooks/useModelState.ts

@@ -1,4 +1,4 @@
-import { useState, useCallback } from "react";
+import { useState, useCallback, useEffect } from "react";
 
 interface UseModelStateProps {
   settingsConfig: string;
@@ -9,39 +9,76 @@ interface UseModelStateProps {
  * 管理模型选择状态
  * 支持 ANTHROPIC_MODEL 和 ANTHROPIC_SMALL_FAST_MODEL
  */
-export function useModelState({
-  settingsConfig,
-  onConfigChange,
-}: UseModelStateProps) {
+export function useModelState({ settingsConfig, onConfigChange }: UseModelStateProps) {
   const [claudeModel, setClaudeModel] = useState("");
-  const [claudeSmallFastModel, setClaudeSmallFastModel] = useState("");
+  const [defaultHaikuModel, setDefaultHaikuModel] = useState("");
+  const [defaultSonnetModel, setDefaultSonnetModel] = useState("");
+  const [defaultOpusModel, setDefaultOpusModel] = useState("");
+
+  // 初始化读取：读新键；若缺失，按兼容优先级回退
+  // Haiku: DEFAULT_HAIKU || SMALL_FAST || MODEL
+  // Sonnet: DEFAULT_SONNET || MODEL || SMALL_FAST
+  // Opus: DEFAULT_OPUS || MODEL || SMALL_FAST
+  // 仅在 settingsConfig 变化时同步一次（表单加载/切换预设时）
+  useEffect(() => {
+    try {
+      const cfg = settingsConfig ? JSON.parse(settingsConfig) : {};
+      const env = cfg?.env || {};
+      const model = typeof env.ANTHROPIC_MODEL === "string" ? env.ANTHROPIC_MODEL : "";
+      const small =
+        typeof env.ANTHROPIC_SMALL_FAST_MODEL === "string" ? env.ANTHROPIC_SMALL_FAST_MODEL : "";
+      const haiku =
+        typeof env.ANTHROPIC_DEFAULT_HAIKU_MODEL === "string"
+          ? env.ANTHROPIC_DEFAULT_HAIKU_MODEL
+          : small || model;
+      const sonnet =
+        typeof env.ANTHROPIC_DEFAULT_SONNET_MODEL === "string"
+          ? env.ANTHROPIC_DEFAULT_SONNET_MODEL
+          : model || small;
+      const opus =
+        typeof env.ANTHROPIC_DEFAULT_OPUS_MODEL === "string"
+          ? env.ANTHROPIC_DEFAULT_OPUS_MODEL
+          : model || small;
+
+      setClaudeModel(model || "");
+      setDefaultHaikuModel(haiku || "");
+      setDefaultSonnetModel(sonnet || "");
+      setDefaultOpusModel(opus || "");
+    } catch {
+      // ignore
+    }
+  }, [settingsConfig]);
 
   const handleModelChange = useCallback(
     (
-      field: "ANTHROPIC_MODEL" | "ANTHROPIC_SMALL_FAST_MODEL",
+      field:
+        | "ANTHROPIC_MODEL"
+        | "ANTHROPIC_DEFAULT_HAIKU_MODEL"
+        | "ANTHROPIC_DEFAULT_SONNET_MODEL"
+        | "ANTHROPIC_DEFAULT_OPUS_MODEL",
       value: string,
     ) => {
-      if (field === "ANTHROPIC_MODEL") {
-        setClaudeModel(value);
-      } else {
-        setClaudeSmallFastModel(value);
-      }
+      if (field === "ANTHROPIC_MODEL") setClaudeModel(value);
+      if (field === "ANTHROPIC_DEFAULT_HAIKU_MODEL") setDefaultHaikuModel(value);
+      if (field === "ANTHROPIC_DEFAULT_SONNET_MODEL") setDefaultSonnetModel(value);
+      if (field === "ANTHROPIC_DEFAULT_OPUS_MODEL") setDefaultOpusModel(value);
 
       try {
-        const currentConfig = settingsConfig
-          ? JSON.parse(settingsConfig)
-          : { env: {} };
+        const currentConfig = settingsConfig ? JSON.parse(settingsConfig) : { env: {} };
         if (!currentConfig.env) currentConfig.env = {};
 
-        if (value.trim()) {
-          currentConfig.env[field] = value.trim();
+        // 新键仅写入；旧键不再写入
+        const trimmed = value.trim();
+        if (trimmed) {
+          currentConfig.env[field] = trimmed;
         } else {
           delete currentConfig.env[field];
         }
+        // 删除旧键
+        delete currentConfig.env["ANTHROPIC_SMALL_FAST_MODEL"];
 
         onConfigChange(JSON.stringify(currentConfig, null, 2));
       } catch (err) {
-        // 如果 JSON 解析失败，不做处理
         console.error("Failed to update model config:", err);
       }
     },
@@ -51,8 +88,12 @@ export function useModelState({
   return {
     claudeModel,
     setClaudeModel,
-    claudeSmallFastModel,
-    setClaudeSmallFastModel,
+    defaultHaikuModel,
+    setDefaultHaikuModel,
+    defaultSonnetModel,
+    setDefaultSonnetModel,
+    defaultOpusModel,
+    setDefaultOpusModel,
     handleModelChange,
   };
 }