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/ShellHighlighter.h

@@ -0,0 +1,11 @@
+// ShellHighlighter.h - simple POSIX shell highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+
+namespace kte {
+class ShellHighlighter final : public LanguageHighlighter {
+public:
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+};
+} // namespace kte