fix: improve type safety and error handling in config-manager

- Wrap JSON.parse in try-catch with clear error message for malformed JSON
- Add iflow, kiro, ghcp providers to CLIProxyVariantConfig type
- Make settings optional in CLIProxyVariantConfig (was required with empty string fallback)
- Remove unsafe type cast in loadConfigSafe()

Addresses additional edge cases from PR #215 code review.

src/types/config.ts

@@ -17,10 +17,10 @@ export interface ProfilesConfig {
  * Example: "flash" → gemini provider with gemini-2.5-flash model
  */
 export interface CLIProxyVariantConfig {
-  /** CLIProxy provider to use (gemini, codex, agy, qwen) */
-  provider: 'gemini' | 'codex' | 'agy' | 'qwen';
-  /** Path to settings.json with custom model configuration */
-  settings: string;
+  /** CLIProxy provider to use */
+  provider: 'gemini' | 'codex' | 'agy' | 'qwen' | 'iflow' | 'kiro' | 'ghcp';
+  /** Path to settings.json with custom model configuration (optional) */
+  settings?: string;
   /** Account identifier for multi-account support (optional, defaults to 'default') */
   account?: string;
   /** Unique port for variant isolation (8318-8417) */

src/utils/config-manager.ts

@@ -121,9 +121,8 @@ export function loadConfigSafe(): Config {
       cliproxy = {};
       for (const [name, variant] of Object.entries(unifiedConfig.cliproxy.variants)) {
         cliproxy[name] = {
-          // Cast provider - unified has more providers than legacy type
-          provider: variant.provider as 'gemini' | 'codex' | 'agy' | 'qwen',
-          settings: variant.settings || '',
+          provider: variant.provider,
+          settings: variant.settings,
           account: variant.account,
           port: variant.port,
         };
@@ -145,7 +144,13 @@ export function loadConfigSafe(): Config {
   }
 
   const raw = fs.readFileSync(configPath, 'utf8');
-  const parsed: unknown = JSON.parse(raw);
+
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(raw);
+  } catch (e) {
+    throw new Error(`Malformed JSON in config: ${configPath} - ${(e as Error).message}`);
+  }
 
   if (!isConfig(parsed)) {
     throw new Error(`Invalid config format: ${configPath}`);