refactor(metadata-protocol): move getDiscovery's body into its facet, and settle the card's last facade-gate rows

.changeset/30147-get-discovery-facet.md

@@ -0,0 +1,11 @@
+---
+'@objectstack/metadata-protocol': patch
+---
+
+refactor(metadata-protocol): `getDiscovery` hands its body to its facet
+
+Clause-②: no
+Metadata-protocol: none
+
+- `ObjectStackProtocolImplementation#getDiscovery` keeps its signature and return type on the class and delegates in one line to `ProtocolDiscoveryAndBasesFacet.getDiscovery`, which holds the body, moved unchanged except for the search probe: the class reads `this.searchAll` on the instance and hands it in, so `capabilities.search` still answers whether this protocol instance serves search. No behaviour changes and nothing to do on upgrade.
+- The published `index.d.ts` and `index.d.cts` carry the same public surface.