✨ feat(lsp_server): implement missing providers and json coverage

Implement workspace configuration/folders and apply WorkspaceEdit.changes.

Strengthen provider JSON coverage (all methods require params, no errors).

Verified: Release test_provider

lsp-server/test/test_provider/test_main.cppm

@@ -8,6 +8,7 @@ import lsp.test.framework;
 import lsp.test.provider.completion;
 import lsp.test.provider.definitions;
 import lsp.test.provider.json_flow;
+import lsp.test.provider.json_provider_coverage;
 import lsp.test.provider.misc;
 import lsp.test.provider.surface;
 import lsp.test.provider.fixtures;
@@ -41,6 +42,8 @@ export int Run(int argc, char** argv)
     lsp::test::provider::DefinitionTests::Register(runner);
     std::cout << "  - JSON flow tests" << std::endl;
     lsp::test::provider::JsonFlowTests::Register(runner);
+    std::cout << "  - JSON provider coverage tests" << std::endl;
+    lsp::test::provider::JsonProviderCoverageTests::Register(runner);
     std::cout << "  - Other provider tests" << std::endl;
     lsp::test::provider::ProviderMiscTests::Register(runner);
     std::cout << "  - Provider surface tests" << std::endl;