Add SQL, Erlang, and Forth highlighter implementations and tests for LSP process and transport handling.

- Added highlighters for new languages (SQL, Erlang, Forth) with filetype recognition.
- Updated and reorganized syntax files to maintain consistency and modularity.
- Introduced LSP transport framing unit tests and JSON decoding/dispatch tests.
- Refactored `LspManager`, integrating UTF-16/UTF-8 position conversions and robust diagnostics handling.
- Enhanced server start/restart logic with workspace root detection and logging to improve LSP usability.

syntax/CppHighlighter.h

@@ -0,0 +1,35 @@
+// CppHighlighter.h - minimal stateless C/C++ line highlighter
+#pragma once
+
+#include <regex>
+#include <string>
+#include <unordered_set>
+#include <vector>
+
+#include "LanguageHighlighter.h"
+
+class Buffer;
+
+namespace kte {
+class CppHighlighter final : public StatefulHighlighter {
+public:
+	CppHighlighter();
+
+	~CppHighlighter() override = default;
+
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+
+	LineState HighlightLineStateful(const Buffer &buf,
+	                                int row,
+	                                const LineState &prev,
+	                                std::vector<HighlightSpan> &out) const override;
+
+private:
+	std::unordered_set<std::string> keywords_;
+	std::unordered_set<std::string> types_;
+
+	static bool is_ident_start(char c);
+
+	static bool is_ident_char(char c);
+};
+} // namespace kte