fix: Claude token rotation, usage-exhausted fallback, and usage API caching

- Fix token rotation not taking effect: getCurrentToken() was shadowed
  by static .env CLAUDE_CODE_OAUTH_TOKEN value in agent environment
- Don't fall back to Kimi on usage-exhausted (only on transient 429/network)
- Add disk cache for Claude usage API data (survives restarts, 429s)
- Rate-limit usage API calls to 1 per token per 5 minutes
- Add ignoreRateLimits option to rotateToken() for exhausted recovery
- Rotate to next token in getActiveProvider() when current is exhausted
- Add isUsageExhausted() helper to provider-fallback

src/agent-runner-environment.ts

@@ -123,9 +123,10 @@ function prepareClaudeEnvironment(args: {
       args.envVars.ANTHROPIC_BASE_URL || process.env.ANTHROPIC_BASE_URL || '';
   }
   {
+    // Token rotation takes priority over static .env value
     const oauthToken =
-      args.envVars.CLAUDE_CODE_OAUTH_TOKEN ||
       getCurrentToken() ||
+      args.envVars.CLAUDE_CODE_OAUTH_TOKEN ||
       process.env.CLAUDE_CODE_OAUTH_TOKEN;
     if (oauthToken) {
       args.env.CLAUDE_CODE_OAUTH_TOKEN = oauthToken;