refactor(metadata-protocol): move the single-record data writes through the protocol host (#25467 E2 section 3)

.changeset/25467-e2-3-data-writes.md

@@ -0,0 +1,10 @@
+---
+'@objectstack/metadata-protocol': patch
+---
+
+refactor(metadata-protocol): the single-record data writes move out of `protocol.ts` through the protocol host
+
+Clause-②: no
+Metadata-protocol: none
+
+No behaviour change. The bodies of `validateData`, `createData`, `updateData` and `deleteData` now live in `protocol-data-writes.ts`, reached through the per-instance host (`protocol-host.ts`). Each method keeps its docblock and signature on `ObjectStackProtocolImplementation`, and each moved body differs from the method body only by `this.` reading `host.`. The published `index.d.ts` (ESM and CJS) is byte-identical to the one `main` builds before this change. Nothing to migrate.