Delete the dead lockedAPI, add UnimplementedCoreAPI for the doubles

cmd/mavweb/handlers_test.go

@@ -17,11 +17,12 @@ import (
 )
 
 // fakeCore records the mutating calls handleTools makes and returns canned
-// tool lists / errors. Embedding ipc.CoreAPI (nil) satisfies the large
+// tool lists / errors. Embedding ipc.UnimplementedCoreAPI satisfies the large
 // interface — only the methods the handlers touch are overridden; any other
-// call would nil-panic, which is fine since the handlers never make them.
+// call returns ipc.ErrNotImplemented instead of nil-panicking, so a test that
+// accidentally exercises an undeclared method fails loudly.
 type fakeCore struct {
-	ipc.CoreAPI
+	ipc.UnimplementedCoreAPI
 
 	proposed, enabled []ipc.Tool
 	listErr           error