.ino sketches get C++ highlighting and code intelligence through Arduino Language Server: completion, signature help, hover, definition navigation and diagnostics. The IDE finds arduino-cli, clangd and the language server installed by Arduino IDE 2 (or paths from languages.arduino settings), reads the board FQBN from sketch.yaml or settings, roots the server at the sketch, and works around the server's capability quirks. Build, upload and serial monitor are left to a plugin.
Co-authored-by: mushketer888 <[email protected]>