FM-PS-LYNX-014 T3: replace callNative overloads with NativeSql

[djwok]

Implements T3 only of FM-PS-LYNX-014 / #34 on current main.

Replaces the four callNative overloads + switch + SAFETY casts with one nativeSql value: promise-returning functions derived from NativePowerSyncModule, each built on withNativeCallback. ADR-0001 public SQL RPC wire (callback open / close / execute / executeBatch) is unchanged. Fake Native Module tests still drive the callback module.

Resulting interface

type NativeSqlFn<T> = T extends (...args: [...infer Args, NativeCallback]) => void
  ? (...args: Args) => Promise<NativeOkEnvelope>
  : never;

export type NativeSql = {
  readonly [K in keyof NativePowerSyncModule]: NativeSqlFn<NativePowerSyncModule[K]>;
};

export const nativeSql: NativeSql = {
  open(payload): Promise<NativeOkEnvelope>;
  close(dbId): Promise<NativeOkEnvelope>;
  execute(dbId, sql, params): Promise<NativeOkEnvelope>;
  executeBatch(dbId, sql, params): Promise<NativeOkEnvelope>;
};

Callers: LynxConnection (execute / executeBatch / close) and LynxDBAdapter.openConnection (open).

Deleted

• Four callNative overloads + implementation signature
• switch (method) dispatcher
• Four SAFETY casts (as OpenPayload, as string, as BindValues, as BindValueRows)

Untouched: PowerSyncDatabase, HTTP transport, NativeSyncHttp, host helper, native Android/iOS, policy/UTF-8/build.

Tests

• Existing fake-module adapter + host tests now call nativeSql.*
• New: all four ops go through callback RPC
• New: missing NativePowerSyncModule throws

Verification

pnpm typecheck, pnpm lint, and pnpm test (108 passing) are green on this revision.

Paste-ready note for #34

Could not comment on #34 from this environment (issue API 403 / not resolvable). Paste:

T3 is up: callNative overloads/switch/SAFETY casts are gone. Adapter SQL now uses nativeSql — a mapped NativeSql of promise functions over withNativeCallback. Wire contract and fake Native Module tests unchanged. PR: #41

Closes the T3 slice of #34 only.