feat(stack): exercise Nacos runtime routing

[XnLemon]

Summary

• deploy Nacos 2.5.1 and bootstrap the owned namespace plus Router binding document
• configure Runtime A/B registration and Router Nacos Config/Naming resolution
• publish exact Release bindings during backend acceptance and assert registered instance metadata
• preserve JSON, SSE, nested invocation, failure-matrix, and Ledger assertions while proving runtime-b-directory was selected
• pin Core and Samples to the exact revisions from their dependent PRs

Validation

• docker compose config --quiet
• go build ./...
• go test ./...
• go test -race ./...
• go vet ./...
• go run ./cmd/manifest-validator components.json
• go test -tags=e2e -count=1 ./tests/backend against real Nacos 2.5.1

Depends on:

• feat(router): add Nacos runtime resolution NeKiro#99
• feat(runtime): register sample runtimes with Nacos NeKiro-Samples#5

Contributes to NeKiro-project/NeKiro#88 and NeKiro-project/NeKiro#89.

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