Register Kestrel with EvalOps agent registry

[haasonsaas]

Summary

• add a Kestrel desktop-agent registration helper for EvalOps agent registry
• register in the background on app startup when an EvalOps token/session exists
• register again immediately after successful EvalOps login so fresh installs appear in the registry without restarting

Validation

• npm ci --ignore-scripts
• npm run build
• git diff --check

[cursor]

PR Summary

Medium Risk
Adds new background network calls to the EvalOps agent registry during app startup and immediately after login, which could impact startup behavior or surface auth/config issues. Failure is handled via warnings, but registration payload/IDs must remain correct to avoid noisy logs or mis-registered agents.

Overview
Registers the Kestrel desktop app as an agent in the EvalOps agent registry.

This introduces a new evalops/registration helper that builds a registration payload (capabilities, surfaces, version, and labels) and calls client.agentRegistry.register, logging when an offline fallback is used. The app now triggers this registration in the background on startup when a token/session exists, and again after a successful evalops:login so new installs appear in the registry without requiring a restart.

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