🛡️ Sentinel: [security improvement] Add strict timeouts and buffer limits to prevent DoS

[thirdbase1]

🚨 Severity: HIGH
💡 Vulnerability: External network requests (AgentConnector) and shell command executions (ShellTool) lacked explicit execution timeouts and buffer/content length limits. This could allow hanging external services or intentionally large payloads to exhaust system resources, leading to a Denial of Service (DoS) vulnerability.
🎯 Impact: If an LLM endpoint or a shell command hung indefinitely, or if it returned massive amounts of data, the agentic process would be exhausted of memory or block indefinitely.
🔧 Fix: Added explicit timeout (30000ms) and maxBuffer/maxContentLength/maxBodyLength limits (1MB) to both the execAsync call and the axios instance to enforce strict boundaries.
✅ Verification: Ran npm run test and npm run build locally, ensuring existing tests still pass and the build succeeds. Tests did not hang, proving limits are safe for expected workloads.

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PR created automatically by Jules for task 17698338774627073693 started by @thirdbase1

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