feat: add registry broker delegation client

[kantorcodes]

Summary

• add typed Registry Broker delegation request/response support
• add coverage for the new /delegate endpoint parsing
• add a runnable delegation example and document it in the examples index

Verification

• go test ./pkg/registrybroker -run 'TestDelegate|TestCovSearchEndpoints|TestCovBuildSearchQuery'
• go test ./examples/registry-broker-delegation
• go run ./examples/registry-broker-delegation

[gemini-code-assist]

Code Review

This pull request introduces the Delegate method to the RegistryBrokerClient, enabling users to request delegation plans for specific tasks. It includes a new runnable example in examples/registry-broker-delegation, comprehensive type definitions for delegation requests and responses, and associated unit tests. Review feedback suggests standardizing CLI error handling in the example by using stderr, expanding test coverage for environment variable utilities, and implementing mechanisms to capture unknown JSON fields for better forward compatibility.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Incremental Changes (commit 743ef84)

Lint-only fixes since last review:

• Range loop: pointer access instead of value copy in main.go
• Parameter shorthand in getEnvOrDefault
• Extracted repeated string literal to const preservedValue in test
• Switched to fmt.Fprintf for test HTTP response writing
• return nil, nil → return JSONObject{}, nil for nil-safety in extractUnknownFields

All previous review findings remain resolved.

Files Reviewed (3 changed files)

• examples/registry-broker-delegation/main.go — lint fix (range loop + param shorthand)
• pkg/registrybroker/delegation_plan_test.go — lint fix (const extraction + fmt.Fprintf)
• pkg/registrybroker/types.go — lint fix (JSONObject{} instead of nil)

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_{Reviewed by mimo-v2-pro-20260318 · 87,873 tokens}