docs(openspec): sync and archive fix-race-doc-and-encoding-gaps

chore(openspec): finalize fix-race-doc-and-encoding-gaps tasks

docs(specs): align project status and fix utf8 readability

fix(grpc-handlers): make streaming tests race-safe

spec: add fix-race-doc-and-encoding-gaps artifacts

docs: fix readme encoding and rename core specs

docs(openspec): archive fix-week15 tracing review change

docs(specs): sync week15 tracing review updates to main specs

fix(tracing): close week15 observability review gaps

docs(openspec): start fix-week15 tracing review gaps change

chore(openspec): archive week14 cluster event bus integration gap fix

docs(spec): sync week14 integration gap deltas into main specs

test(runtime): add cross-node publish-to-stream regression coverage

fix(cluster): scope transfer dedupe by shard and workload

fix(cluster): enforce explicit backend support and emulation gate