feat(agy): add preflight quota check with auto-switch

Before launching Claude CLI for Antigravity, check if current account
has remaining quota. If exhausted, auto-switch to alternative account
with available quota. Prevents session failures mid-use.

src/cliproxy/cliproxy-executor.ts

@@ -58,6 +58,7 @@ import {
 import { detectRunningProxy, waitForProxyHealthy, reclaimOrphanedProxy } from './proxy-detector';
 import { withStartupLock } from './startup-lock';
 import { loadOrCreateUnifiedConfig } from '../config/unified-config-loader';
+import { fetchAccountQuota, findAvailableAccount } from './quota-fetcher';
 
 /** Default executor configuration */
 const DEFAULT_CONFIG: ExecutorConfig = {
@@ -463,6 +464,40 @@ export async function execClaudeWithCLIProxy(
     }
   }
 
+  // 3b. Preflight quota check - auto-switch to account with quota before launch
+  // Only for agy (Antigravity) which has quota tracking
+  if (provider === 'agy') {
+    const defaultAccount = getDefaultAccount(provider);
+    if (defaultAccount) {
+      log(`Checking quota for ${defaultAccount.email || defaultAccount.id}`);
+      const quota = await fetchAccountQuota(provider, defaultAccount.id);
+
+      // Check if current account is exhausted (no model with >5% quota)
+      const hasQuota = quota.success && quota.models.some((m) => m.percentage > 5);
+
+      if (!hasQuota && quota.success) {
+        // Current account exhausted, try to find alternative
+        log('Current account quota exhausted, searching for alternatives...');
+        const alternative = await findAvailableAccount(provider, defaultAccount.id);
+
+        if (alternative) {
+          // Auto-switch to account with remaining quota
+          setDefaultAccount(provider, alternative.account.id);
+          touchAccount(provider, alternative.account.id);
+          console.log(
+            info(
+              `Auto-switched to ${alternative.account.email || alternative.account.id} (current account quota exhausted)`
+            )
+          );
+        } else {
+          // No alternatives available - warn but continue
+          console.log(warn('All accounts appear quota-exhausted'));
+          console.log(`    Run: ccs cliproxy doctor`);
+        }
+      }
+    }
+  }
+
   // 4. First-run model configuration (interactive)
   // For supported providers, prompt user to select model on first run
   // Pass customSettingsPath for CLIProxy variants