Publish alpha module release chain

[nucleuskit]

Summary

• Remove the remaining root replace directive and pin github.com/nucleuskit/contract to v0.1.0-alpha.3.
• Advance submodule pointers to published alpha module tags for cap, bridge, and runtime modules.
• Update nucleus init service templates to use published http, cap, and core alpha tags, including checksums, and align with runtimehttp.Server.Handler().
• Add an implementation status document that distinguishes implemented, scaffold, metadata-only, fake/static, and published alpha surfaces.

Why

This closes the no-local-replace release path for public Nucleus modules and makes generated services build against the published HTTP runtime instead of an old pseudo-version.

Validation

• GOWORK=off go test ./... in root, core, cap, contract, runtime/http, runtime/grpc, runtime/worker, bridge, and bridge/nacosofficial.
• rg -n '^replace ' --glob 'go.mod' . returned no matches.
• rg -n 'github\.com/nucleuskit/nucleus/(core|cap|bridge|runtime)' --glob '*.go' --glob 'go.mod' bridge cap core contract runtime cmd returned no matches.
• go list -m -versions confirmed the published alpha tags for core, cap, contract, http, grpc, worker, bridge, and bridge/nacosofficial.

Residual Risk

The root CLI module remains pre-alpha and is not tagged in this PR. The runtime and bridge modules are published as alpha tags, but broader production replacement confidence still depends on more real-service validation.