[refactor] Consolidate settings migration logic into dedicated utility

- Extract all migrateDeprecatedValue logic from individual settings into centralized settingsMigration.ts
- Remove migrateDeprecatedValue from SettingParams interface and coreSettings definitions
- Simplify settingStore by removing tryMigrateDeprecatedValue function
- Ensure migrations run after loadSettingValues() for clean initialization flow
- Update tests to reflect new migration approach

This refactor centralizes all setting value migrations in one place, making them easier to maintain and avoiding timing issues with settings that don't exist yet.

src/stores/settingStore.ts

@@ -20,10 +20,6 @@ export interface SettingTreeNode extends TreeNode {
   data?: SettingParams
 }
 
-function tryMigrateDeprecatedValue(setting: SettingParams, value: any) {
-  return setting?.migrateDeprecatedValue?.(value) ?? value
-}
-
 function onChange(setting: SettingParams, newValue: any, oldValue: any) {
   if (setting?.onChange) {
     setting.onChange(newValue, oldValue)
@@ -54,16 +50,12 @@ export const useSettingStore = defineStore('setting', () => {
   async function set<K extends keyof Settings>(key: K, value: Settings[K]) {
     // Clone the incoming value to prevent external mutations
     const clonedValue = _.cloneDeep(value)
-    const newValue = tryMigrateDeprecatedValue(
-      settingsById.value[key],
-      clonedValue
-    )
     const oldValue = get(key)
-    if (newValue === oldValue) return
+    if (clonedValue === oldValue) return
 
-    onChange(settingsById.value[key], newValue, oldValue)
-    settingValues.value[key] = newValue
-    await api.storeSetting(key, newValue)
+    onChange(settingsById.value[key], clonedValue, oldValue)
+    settingValues.value[key] = clonedValue
+    await api.storeSetting(key, clonedValue)
   }
 
   /**
@@ -102,12 +94,7 @@ export const useSettingStore = defineStore('setting', () => {
 
     settingsById.value[setting.id] = setting
 
-    if (settingValues.value[setting.id] !== undefined) {
-      settingValues.value[setting.id] = tryMigrateDeprecatedValue(
-        setting,
-        settingValues.value[setting.id]
-      )
-    }
+    // Trigger onChange callback with current value
     onChange(setting, get(setting.id), undefined)
   }