fix: dead code and minor issues in src/agent/react.js

[avoidwork]

Summary

Audit of src/agent/react.js identified 4 issues including an unused _lastError variable in both callReactAgent and callReactAgentStreaming, inconsistent indentation, silent role mapping in message rebuild, and a fallback role that could mask unexpected message types.

Environment

• OS: Linux 7.0.2-7-pve
• Node.js: v25.8.1
• madz version: 1.12.0
• LLM provider: Unknown — user to confirm

Reproduction

1. Run audit-code on ./src/agent directory
2. Review audit output for react.js
3. Observe 4 issues reported

Expected Behavior

Clean codebase with no dead code, consistent formatting, and proper error tracking.

Actual Behavior

4 issues found:

• 1 medium: unused _lastError variable in both callReactAgent and callReactAgentStreaming
• 3 low: inconsistent indentation, silent role mapping in message rebuild, fallback role masking

Additional Context

The file contains 529 lines and is the core agent implementation. The unused _lastError variables suggest incomplete error tracking or leftover from refactoring. The other issues are minor code quality concerns.

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Audit Table

File	Line	Type	Severity	Summary
react.js	131, 301	Bug	Medium	Unused _lastError variable in both callReactAgent and callReactAgentStreaming — never read or logged
react.js	143-151	Style	Low	Inconsistent indentation in cache logic block after extractContent
react.js	190-197, 494-501	Bug	Low	Silent role mapping in message rebuild — tool messages from compactConversation would be silently mapped to AIMessage
react.js	24	Security	Low	getMessageRole falls back to system for unknown message types — could mask unexpected message types

Summary: 4 issues found (0 critical, 0 high, 1 medium, 3 low). 1 file audited.