feat(lsp): add LSP server with completion, definition, hover, diagnostics

Makefile

@@ -5,7 +5,7 @@ BUILD_DIR := build
 
 EXAMPLES := hello fibonacci factorial structs enums methods algebraic_enums generics generics_struct generic_infer generic_infer2 extend_generic pattern_matching strings strings2 map result_option try_operator ownership ctfe async concurrency os_time process json iter
 
-.PHONY: all build dev debug test clean clean-all test-examples selfhost test-golden selfhost-loop
+.PHONY: all build dev debug test clean clean-all test-examples selfhost test-golden selfhost-loop lsp
 
 all: build
 
@@ -132,3 +132,9 @@ selfhost-loop: build
 		echo "  C output was identical — ELF difference is likely linker non-determinism"; \
 		echo "=== Selfhost loop: C codegen deterministic ✓, ELF non-deterministic (expected) ==="; \
 	fi
+
+lsp: tools/bux-lsp
+	@echo "LSP server ready at tools/bux-lsp"
+
+tools/bux-lsp: tools/lsp_server.nim
+	cd tools && $(NIM) c -o:bux-lsp lsp_server.nim