[godronus]

Summary

Base feat/db-interface-async (#9), with feat/db-interface-kv (#10) merged in. Until #10 merges, this diff also shows the kv-types + kv-sync commits. The new parts are the merge and 09f4443.

• deps/db/kv.wit: interface gcore:db/kv, the async variant of kv-sync. database.execute(op) and batch(ops) return future-op-result / future-batch-result (subscribe() -> pollable, get(), result returned once). open stays synchronous. Reuses kv-types op / op-result.
• world reactor-async imports gcore:db/kv@0.1.0 beside gcore:db/sql; world reactor is unchanged (kv-sync).

The WIT documents the ordering rule: calls already started run independently. Read-your-writes holds for a call started after an earlier call's result is ready. Dropping a future abandons the result, and the operation may or may not have been applied.

Decisions needed

#	Decision	Proposal
1	execute(op) instead of a method per op	Two future types instead of seven; maps 1:1 onto the host's KvBackend::execute. The SDKs keep get, set, ... on top
2	Ship async KV for JS	Yes, as for SQL: Promise.all of 3 gets takes 48 ms, against 147 ms awaited in turn

Engine design + measurements: docs/db/KV_ASYNC.md in G-Core/FastEdge (branch feat/db-interface-kv-async).

Related: #9 (base), #10 (merged in), G-Core/FastEdge#662, G-Core/FastEdge-sdk-js#159