Add Config updates via SSE

[timokoessler]

Extracted from #984

Summary by Aikido

⚠️ Security Issues: 2	🔍 Quality Issues: 7	✅ Resolved Issues: 1

🚀 New Features

• Implemented SSE-based config updates with connection and parsing

⚡ Enhancements

• Probed realtime endpoint and fell back to polling when unreachable

🔧 Refactors

• Extended poll/getConfigLastUpdatedAt APIs to accept realtime URL
• Adjusted Undici tests to wait for realtime probe before assertions
• Made test helper match accept variadic arguments and forward them

^{More info}

[codecov]

Codecov Report

❌ Patch coverage is 79.18216% with 112 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
library/helpers/eventsource-parser/parse.ts	68.82%	53 Missing ⚠️
library/agent/realtime/listenForConfigUpdates.ts	49.29%	36 Missing ⚠️
library/helpers/eventsource-parser/errors.ts	56.52%	10 Missing ⚠️
library/agent/realtime/connectToSSE.ts	96.55%	6 Missing ⚠️
library/agent/Agent.ts	88.88%	4 Missing ⚠️
library/agent/realtime/probeRealtimeURL.ts	93.18%	3 Missing ⚠️

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