refactor(runtime): use public SDK registration

[XnLemon]

Summary

• migrate Runtime A and Runtime B to public agent/registration/nacos
• remove the Samples-owned registration adapter and Runtime B wrappers
• preserve Agent-owned challenge, authentication, readiness, handler, and host wiring
• add A/B composition tests for disabled and fail-closed Nacos modes
• remove 1,283 lines of duplicate registration implementation/tests
• update Runtime B CI after removing the migrated package path

Closes #13
Depends on NeKiro-project/nekiro-sdk-go#6.

Exact revisions

• Core: b588c754e369c6ae09dd415870d7ce111858af12
• SDK: 48d495894a5e22fa3c7ceee483e8a62025e5bcfa

Validation

• go build ./...
• go test -count=1 ./...
• go test -race ./...
• go vet ./...
• go mod tidy
• go mod verify
• git diff --check

Local Docker image builds were not run because the Docker Desktop Linux daemon is not running. Required CI owns both Runtime image builds.

Fallback report

Fallback delta: removed 0, retained 0, added 0, net 0
Added fallback evidence: none

[XnLemon]

LGTM on current HEAD 80bf8e18531ad594f34996f573fbdd81aa5496f9.

I re-reviewed both Runtime entrypoints, disabled/Nacos composition, readiness and host lifecycle wiring, the removal of duplicate adapters/wrappers, documentation, dependency pins, and CI package ownership. The stale internal/nacosregistration workflow path was a valid required-closure issue and is fixed in this HEAD. No actionable findings remain.

Validation evidence: local build/test/race/vet/mod verification passed; CI Runtime A, Runtime B, images, security, and required checks are green.

中文

已复核当前 HEAD 80bf8e18531ad594f34996f573fbdd81aa5496f9，LGTM。

我重新检查了两个 Runtime 入口、disabled/Nacos 组合、readiness 与 host 生命周期接线、重复 adapter/wrapper 删除、文档、依赖固定和 CI 包归属。workflow 中残留的 internal/nacosregistration 路径是有效的 required-closure 问题，已在当前 HEAD 修复。没有剩余可执行问题。

验证证据：本地 build/test/race/vet/mod verification 均通过；CI Runtime A、Runtime B、images、security 和 required 全绿。

[XnLemon]

LGTM