Add local-first execution contracts to the capability language

src/query/compile.ts

@@ -128,6 +128,23 @@ export async function compileQuery(
     const member = contract.members.find((entry) => entry.displayName === name);
     if (!member || member.kind === "operation" || !member.queryRead)
       return fail("QUERY_FIELD_NOT_QUERYABLE", `${contract.displayName}.${name} is not queryable`, node);
+    if (declaration.placement?.kind === "local") {
+      const getter = member.operations.find(
+        (operation) => operation.displayName === (member.kind === "value" ? "get" : "resolve"),
+      );
+      if (getter?.execution?.kind !== "snapshot" || !getter.execution.targets.includes("browser"))
+        fail(
+          "QUERY_LOCAL_DEPENDENCY",
+          `Local query requires a browser snapshot getter for ${contract.displayName}.${name}; split the remote field or move the query to the server`,
+          node,
+        );
+      if (member.queryRead.execution === "rpc-permitted")
+        fail(
+          "QUERY_LOCAL_DEPENDENCY",
+          `Local query cannot include remote-compute field ${contract.displayName}.${name}`,
+          node,
+        );
+    }
     const key = `${id}\0${member.id}`;
     const effect = effects.get(key) ?? {
       interfaceRevisionId: id,