LSP: Implement Phase 4 Endpoints

| Name | Type | Direction | Category | Priority / Dev phase | Supported by FSAC | Note |
| ---------------------------------------- | ------------ | --------- | --------------------------------- | -------------------- | ----------------- | ------------------------------------------------- |
| `textDocument/willSave` | Notification | ➡️ | Document synchronization | 4 | | |
| `textDocument/willSaveWaitUntil` | Request | ↩️ | Document synchronization | 4 | | |
| `codeAction/resolve` | Request | ↩️ | Language features | 4 | | |
| `codeLens/resolve` | Request | ↩️ | Language features | 4 | ✅ | |
| `inlayHint/resolve` | Request | ↩️ | Language features | 4 | | |
| `textDocument/codeAction` | Request | ↩️ | Language features | 4 | ✅ | |
| `textDocument/codeLens` | Request | ↩️ | Language features | 4 | ✅ | |
| `textDocument/prepareRename` | Request | ↩️ | Language features | 4 | | |
| `textDocument/publishDiagnostics` | Notification | ⬅️ | Language features | 4 | ✅ | |
| `workspace/codeLens/refresh` | Request | ↪️ | Language Features | 4 | ✅ | |
| `window/showMessage` | Notification | ⬅️ | Window Features | 4 | ✅ | |
| `workspace/configuration` | Request | ↪️ | Workspace Features | 4 | | |
| `workspace/diagnostic` | Request | ↩️ | Workspace Features | 4 | | |
| `workspace/didChangeConfiguration` | Notification | ➡️ | Workspace Features | 4 | ✅ | |
| `workspace/symbol` | Request | ↩️ | Workspace Features | 4 | ✅ | |
| `workspaceSymbol/resolve` | Request | ↩️ | Workspace Features | 4 | | |